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Sago Palm bloom with foliage - Cycas Revoluta

Sago Palm bloom with foliage - Cycas Revoluta

Gymnosperm Stem: Cork and Cortex in Three Year Pinus

cross section: Pinus stem magnification: 100x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts. cross section: Pinus stem magnification: 100x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts.

Welwitschia Plant

Welwitschia Plant

Gymnosperm Stem: Cork in Three Year Pinus

cross section: Pinus stem magnification: 400x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. cross section: Pinus stem magnification: 400x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins.

Ephedra

Welwitschia seeds

Welwitschia seeds

Welwitschia plant

Welwitschia plant

Gymnosperm Stem: Medullary Rays Three Year Pinus

cross section: Pinus stem magnification: 100x Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. cross section: Pinus stem magnification: 100x Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem.

Gymnosperm Stem: Three Year Pinus

cross section: Pinus stem magnification: 40x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts. cross section: Pinus stem magnification: 40x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts.

Gymnosperm Stem: Resin Duct in Three Year Pinus

cross section: Pinus stem magnification: 100x Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. cross section: Pinus stem magnification: 100x Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem.

Welwitschia Plant

Welwitschia Plant

Pinus kesiya, one of gymnosperm plant. Pinus kesiya, one of gymnosperm plant.

Gymnosperm Stem: Cortical Resin Duct in Three Year Pinus

cross section: Pinus stem magnification: 100x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts. cross section: Pinus stem magnification: 100x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts.

Welwitschia seeds

Welwitschia seeds

Gymnosperm Stem: Annual Rings in Three Year Pinus

cross section: Pinus stem magnification: 100x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts. cross section: Pinus stem magnification: 100x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts.

Life Cycle of Pine Tree: reproduction of gymnosperms with titles

Life Cycle of Pine Tree: reproduction of gymnosperms with titles

New leaf of a cycad, ready to unfurl. New leaf of a cycad, ready to unfurl

Gymnosperm Stem: Three Year Pinus

cross section: Pinus stem magnification: 100x Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. cross section: Pinus stem magnification: 100x Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem.

Close-up of pine tree bark. Background or wallpaper. Close-up of pine tree bark. Background or wallpaper.

Gymnosperm Stem: Medullary Rays in Three Year Pinus

cross section: Pinus stem magnification: 100x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts. cross section: Pinus stem magnification: 100x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts.

Close-up on ginkgo biloba tree leaves

Gymnosperm Stem: Cambium in Two Year Pinus

cross section: Pinus stem magnification: 400x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts. cross section: Pinus stem magnification: 400x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts.

Gymnosperm Stem: Two Year Pinus

cross section: Pinus stem magnification: 40x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts. cross section: Pinus stem magnification: 40x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts.

Gymnosperm Stem: Pith in Two Year Pinus

cross section: Pinus stem magnification: 400x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts. cross section: Pinus stem magnification: 400x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts.

Welwitschia mirabilis, a Gymnosperm endemic to the Namib desert

Welwitschia mirabilis, a Gymnosperm endemic to the Namib desert

Gymnosperm vs angiosperm vector illustration. Labeled educational scheme.

Gymnosperm vs angiosperm vector illustration. Labeled educational scheme.

Gymnosperm Stem: Phloem in Three Year Pinus

cross section: Pinus stem magnification: 100x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts. cross section: Pinus stem magnification: 100x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts.

Close-up on ginkgo biloba tree leaves

Green leaves and male cone of Cycas revoluta, a species of gymnosperm in the family Cycadaceae. Cycas is a genus of plants

Green leaves and male cone of Cycas revoluta, a species of gymnosperm in the family Cycadaceae. Cycas is a genus of plants

Ancient medicinal plant Ephedra

Ancient medicinal plant Ephedra

Welwitschia Plant

Welwitschia Plant

Gymnosperm Stem: Pith in Three Year Pinus

cross section: Pinus stem magnification: 100x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts. cross section: Pinus stem magnification: 100x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts.

Gymnosperm Stem: Epidermis and Cortex in Two Year Pinus

cross section: Pinus stem magnification: 400x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. cross section: Pinus stem magnification: 400x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous.

Gymnosperm Stem: Two Year Pinus

cross section: Pinus stem magnification: 100x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts. cross section: Pinus stem magnification: 100x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts.

Life Cycle of Pine Tree: reproduction of gymnosperms

Life Cycle of Pine Tree: reproduction of gymnosperms

Gymnosperm Stem: Three Year Pinus

cross section: Pinus stem magnification: 40x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts. cross section: Pinus stem magnification: 40x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts.

Gymnosperm Stem: Cambium in Three Year Pinus

cross section: Pinus stem magnification: 400x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts. cross section: Pinus stem magnification: 400x During the first year of growth the cutinized epidermis is replaced by protective growth of cork rich periderm. The outer periderm consists of layers of cork cells, the phellem, which produces waterproofing suberin. Cork cells are dead at maturity. Deep to the phellem is a living layer of cork cambium or phellogen and beneath that, layers of cork parenchyma or phelloderm. Many cells in the periderm contain dark staining tannins. The cortex is divided into a thin outer hypodermis of lignified sclerenchyma cells and thicker inner cortex of thin walled parenchyma cells containing chloroplasts. Large resin ducts are surrounded by secretory parenchyma that produces resins and turpentines. Some cells enlarge into dark staining tyloses. Both endoderm and pericycle are inconspicuous. The vascular cylinder or stele in young stems consists of a ring of vascular bundles interspaced with medullary rays of parenchyma cells. Seasonal activity of the cambium replaces the isolated vascular bundles with well-defined annual rings of secondary phloem and xylem. Xylem is endarch with protoxylem found towards center of the stem and younger metaxylem towards the periphery of the stem. Protoxylem consists of annular and spiral tracheids with only tracheids found in metaxylem. True xylem vessels are lacking. Because of the greater production of xylem, the vascular cylinder is dominated by radially arranged rays of secondary xylem interspaced with medullary rays of parenchyma cells. Conspicuous resin ducts are present throughout the xylem. Phloem is endarch but annual growth the of stem makes it difficult to distinguish between older protophloem to the periphery and younger metapholem towards center of the stem. Phloem lacks companion cells, consisting entirely of sieve tubes and phloem parenchyma. Medullary rays in the secondary phloem include protein rich albuminous cells. A well-defined pith of parenchyma cells is interrupted by a few large resin ducts.

Welwitschia Mirabilis

Welwitschia Mirabilis

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