. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. VELAMEN. 227 lamina, and in the pitchers 2-3 layers of cells below the surface. They are never continuous with the vascular bundles. In the stem they are all arranged parallel to its axis; in the leaf, at least in the wall of the pitcher-shaped portion, they point irregularly in different directions. In the base of the leaf of the Isoeteae ^ are found series of short spiral tracheides, having the same form as those of the xylem in the stem of these plants : they occur in the dense mass of parenc
. Comparative anatomy of the vegetative organs of the phanerogams and ferns;. Plant anatomy; Ferns. VELAMEN. 227 lamina, and in the pitchers 2-3 layers of cells below the surface. They are never continuous with the vascular bundles. In the stem they are all arranged parallel to its axis; in the leaf, at least in the wall of the pitcher-shaped portion, they point irregularly in different directions. In the base of the leaf of the Isoeteae ^ are found series of short spiral tracheides, having the same form as those of the xylem in the stem of these plants : they occur in the dense mass of parenchyma at the point of insertion of the membranous ligula, called by Braun the Glossopodium. They extend from the upper and lower margins of this body almost horizontally to the inner surface of the base of the leaf: those of the upper side towards the posterior wall, those of the under side towards the mem- branous lip-like lower margin of the depression in which the ligule is seated. They have no connection with the vascular bundle of the leaf. Sect. 56. A continuous layer of air-containing tracheides covers, as a sheaik or â uelamen, the aerial roots of epiphytic orchids, which in this respect resemble those of some other plants, A especially Aroideae. The tracheal sheath of the roots of Orchids is produced from the layer of dermatogen, which, according to Treub 'â ', in Vanilla and Stanhopea, is differentiated close behind the growing-point from a common initial group for the root-cap and the body of the root: this I found to be the case in Vanda furva, while in species of Oncidium (Fig. 90, 91) the dermatogen passes over the growing-point as a distinct layer between periblem and calyptrogen. The simple layer of the periblem, adjoining the dermatogen internally, develops into the endoder- mis, which consists of longitudinal rows of alter- nately elongated and short cells (comp. p. 125). The very delicate cuticle which is present at first, i. e. where the root emerges from t
Size: 1157px × 2158px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecad, booksubjectplantanatomy, bookyear1884
