Fig. 88.—A Simple Netted-veined Leaf.
Fig. 89.—A Simple Parallel-veined Leaf.
Fig. 90.—Compound or Branched Leaf of Brake (a common fern).
Kinds.—Leaves are simple or unbranched (Figs. [88], [89]), and compound or branched (Fig. [90]). The method of compounding or branching follows the mode of veining. The veining, or venation, is of two general kinds. In some plants the main veins diverge, and there is a conspicuous network of smaller veins; such leaves are netted-veined. They are characteristic of the dicotyledons. In other plants the main veins are parallel, or nearly so, and there is no conspicuous network; these are parallel-veined leaves (Figs. [89], [102]). These leaves are the rule in monocotyledonous plants. The venation of netted-veined leaves is pinnate or feather-like when the veins arise from the side of a continuous midrib (Fig. [91]); palmate or digitate (hand-like) when the veins arise from the apex of the petiole (Figs. [88], [92]). If leaves were divided between the main veins, the former would be pinnately and the latter digitately compound.
Fig. 91.—Complete Leaves of Willlow.
