Text-book of botany, morphological and physiological . own bundles ofsclerenchyma. They have no-thing in common with the fibro-vascular bundles, but are only apeculiar form of the fundamentaltissue which also often occurselsewhere in Cryptogams in pro-senchymatous forms. The ten-dency to prosenchymatous de-velopment of the cells of thefundamental tissue occurs alsoespecially in the stems of Lyco-podiacese. In Selaginella denti-culata (Fig. 87, y^) the axial fibro-vascular bundle is surroundedby a very loose parenchymawhich forms large intercellularspaces ; this innermost portion of the fundame
Text-book of botany, morphological and physiological . own bundles ofsclerenchyma. They have no-thing in common with the fibro-vascular bundles, but are only apeculiar form of the fundamentaltissue which also often occurselsewhere in Cryptogams in pro-senchymatous forms. The ten-dency to prosenchymatous de-velopment of the cells of thefundamental tissue occurs alsoespecially in the stems of Lyco-podiacese. In Selaginella denti-culata (Fig. 87, y^) the axial fibro-vascular bundle is surroundedby a very loose parenchymawhich forms large intercellularspaces ; this innermost portion of the fundamental tissue is enveloped by a thin-walled tissue without interstices, which shows itself on longitudinal section to be deve-loped prosenchymatously; the cells are pointed above and below, and penetrate to aconsiderable distance between one another; towards the circumference they becomegradually narrower and more pointed ; the outermost are dark-walled and form theepidermal system which gradually passes over into this fundamental tissue. In Lycopodium. Fig. Z-j.—A transverse section of the stem oi Selaginella dentictdata; thefibro-vascular bundle is not yet fully developed; the vessels are already lignifiedon both sides, but not yet in the centre; / air-conducting intercellular spacesin the parenchyma enveloping- the bundle; towards b the part of the tissuecorresponding to the bundle which bends outwards to the leaf. R transversesection of the mature stem of LycopodiH??t cha7nc?cyparisstis, the axial tissue-cylinder consists of densely crowded and coalescent fibro-vascular bundles ; thefour parts of their xylem are quite separated, forming four bands on the trans-verse section, between and around which are found the narrower cells of thephloem. The phloem portions of the four bundles have coalesced ; between eachpair of xylem-bundles is seen a row of wider cells, the latticed cells or sieve-tubes ; the narrow cells lying on the right and left edge of each xylem portionare spir
Size: 1235px × 2024px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
