. The botanical class-book, and flora of Pennsylvania, designed for seminaries of learning and private classes. petiole runs directly throughthe middle of the blade to the apex, giving off at intervalslateral veinlets, as in the Beech, Chestnut, &c. In radiate-veined leaves (Fig. 23) the vessels divide at the apex of thepetiole into three or more portions or ribs of nearly equal size,which are usually divergent, each giving off veins andveinlets like the single rib of a feather-veined leaf. FORM OF LEAVES. 101. The form of leaves may be considered to dependupon the distribution of th
. The botanical class-book, and flora of Pennsylvania, designed for seminaries of learning and private classes. petiole runs directly throughthe middle of the blade to the apex, giving off at intervalslateral veinlets, as in the Beech, Chestnut, &c. In radiate-veined leaves (Fig. 23) the vessels divide at the apex of thepetiole into three or more portions or ribs of nearly equal size,which are usually divergent, each giving off veins andveinlets like the single rib of a feather-veined leaf. FORM OF LEAVES. 101. The form of leaves may be considered to dependupon the distribution of the veins, and the quantity ofparenchyma. Since it is through the veins alone that the-nutriment is conveyed for the development and extension of FOKM OF LEAVES. 33 the leaf, it follows that there will be the greatest extensionof outline where the veins are largest and most numerous. FEATHER-VEINED LEAVES. 102. If the principal vein of a feather-veined leaf arenot greatlyprolonged, and are somewhat equal in length, theblade will have a more or less elongated form. 25. Middle veinlets longest. 26. 27.
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