. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. 114 CONNECTION BETWEEN TEAF AND STEM opening towards the concave or flattened upper surface and with the protoxylems directed uiwards (Fig. 54, A-D). The part of the ground-tissue inchided within tire group of strands is spoken of as pitli, and that outside as cortex, the peripheral laj/ers of the latter not uncommonly consisting of mechanical tissue (Fig. 54, Sc). The bundles of the petiole can be traced backwards some little distance into the cortex of the stem, following a slightly oblique course, so that,
. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. 114 CONNECTION BETWEEN TEAF AND STEM opening towards the concave or flattened upper surface and with the protoxylems directed uiwards (Fig. 54, A-D). The part of the ground-tissue inchided within tire group of strands is spoken of as pitli, and that outside as cortex, the peripheral laj/ers of the latter not uncommonly consisting of mechanical tissue (Fig. 54, Sc). The bundles of the petiole can be traced backwards some little distance into the cortex of the stem, following a slightly oblique course, so that, in sections cut transversel}' just below the nodes, the one or more bundles {leaf-trace bundles) passing from the leaf into the stem appear cut ''*W^ \ ^ W^ obliquely in the cortex. After penetrating \ '1 . r;'I #7 some little way into the latter the bundles turn abruptly downwards and run vertically through one or more intcrnodes, ultimately, with (Fig. 55) or without previous branch- ing, fusing laterally with strands derived from other leaves. The bundles traversing the stem are therefore merely downward continuations of those found in the leaves, the bundles of stem and leaf are common. The vascular strands passing to the axillary buds (cf. Fig. 69, p. 142) are branches of those serving the leaves, whilst the vascular supply of stipules originates in a similar manner. In Monocotyledons, where the sheathing leaf-bases completely encircle the axis, numerous strands pass from each leaf into the stem. The median \-ascular bundles pass almost to the centre of the stem before thej' bend downwards ; subsequently they pursue a longitudinal direction, at the same time returning obliquely towards the periphery. The more laterally placed strands follow a similar course, but do not penetrate to the same depth. As a result the vascular bundles from the successive leaves usually appear irregularly scattered through the cross-. FiG. 55.—Diagram- matic representa- tion of the vas-
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