. Introduction to structural and systematic botany, and vegetable physiology. Botany. THEIR VENATION. 155 277. Parallel-veined or nerved leaves are characteristic of En- dogenous plants; while reticulated leaves are ahnost universal in. Exogenous plants. We are thus furnished with a very obvious, al- though by no means absolute, distinction between these two great classes of plants, independently of the structure of their stems (198). 278. In reticulated leaves, the coarse primary veins (one or more in number), which proceed immediately from the apex of the petiole, are called ribs; the branch
. Introduction to structural and systematic botany, and vegetable physiology. Botany. THEIR VENATION. 155 277. Parallel-veined or nerved leaves are characteristic of En- dogenous plants; while reticulated leaves are ahnost universal in. Exogenous plants. We are thus furnished with a very obvious, al- though by no means absolute, distinction between these two great classes of plants, independently of the structure of their stems (198). 278. In reticulated leaves, the coarse primary veins (one or more in number), which proceed immediately from the apex of the petiole, are called ribs; the branches are termed veins, and their subordinate ramifications, veinlets. Very frequently, a single strong rib (called the midrib), forming a continuation of the petiole, runs directly through the middle of the blade to the/&pex (Fig. 229, 238, (fee), and from it the lateral veins all diverge. Such leaves are termed feather-veined or pinnately veined; and are subject to vari- ous modifications, according to the arrangement of the veins and vein- lets ; the primary veins sometimes passing straight from the midrib to the margin, as in the Beech and Chestnut (Fig. 238) ; while in other cases they are divided into veinlets long before they reach the margin. When the midrib gives off a very strong primary vein or branch on each side above the base, the leaf is said to be triph- ribbed, or often tripli-nerved, as in the common Sunflower (Fig. riQ. 229. A leaf of the Quince, of the nctted-Teined or reticulated sort: 6, blade: p, petiole or leaf-stalk! si, stipules. FIG. 230. Parallel-Teined leaf of the Lily of the Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Gray, Asa, 1810-1888. New York [etc. ] Ivison, Blakeman, Taylor & Co.
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