. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. AOKOGENOUS OE AOOTYLEDONOUS STEM. 71 to the meshes seen in the liber of Exogens (fig. 119). In these spaces vessels of communication pass between the outer or cortical, and the inner or central portions of the stem. Prom the point where the vascular bundles unite or anastomose, other vessels are given off to supply the fronds, ajad some pass into the ad- ventitious roots, which are often pro- duced abundantly on the outside of the stipe (fig. 135 ra). The trunk of the
. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. AOKOGENOUS OE AOOTYLEDONOUS STEM. 71 to the meshes seen in the liber of Exogens (fig. 119). In these spaces vessels of communication pass between the outer or cortical, and the inner or central portions of the stem. Prom the point where the vascular bundles unite or anastomose, other vessels are given off to supply the fronds, ajad some pass into the ad- ventitious roots, which are often pro- duced abundantly on the outside of the stipe (fig. 135 ra). The trunk of the Acrogen dififersfrom that of the Exogen, by having its. Fig, 136. « vascular cylinder penetrated by only one kind of horizontal tissue, namely, the vascular bundles belonging to the fronds; while the Exogen has in addi- tion another horizontal tissue, namely, meduUary rays, composed of cellular tissue, and performing a totally difierent function. The acrogenous stem in the young state is solid, but it frequently be- comes hollow in the progress of. Kg. 135. growth, by the rupture and absorp- Fig. 135. Tree fem {AlsopJiUa perroteticma), of the East Indies. Stem or^tipe is cylindrical, unbranched, and presents at its base, r a, a conical enlargement, formed by a mass of adventitious roots. The leaves are terminal, and in the young state are rolled up in a circinate manner. Fig. 136. Transverse section of the stem of a Tree Um(Cyatliea). m. Cellular tissue, corresponding to pith, occupying the central part, s I, Vascular circle composed of numerous irregularly-formed masses. /, Darlc-coloured woody or prosenchy- matous fibres, forming the borders of the vascular masses, v v, Pale-coloured vessels, chiefly scalariform, occupying the centre of the masses, p. Parenchymatous or cellular external zone, communicating with the central portion, e. Hard epidermal envelope, occupying the place of the Please note that these images are extracted from scanned page images that may have
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
