. Class-book of botany : being outlines of the structure, physiology and classification of plants : with a flora of the United States and Canada . Botany; Botany; Botany. 64 FOEM OB FIGUBB. 269. Of the reticulate venation, the student should carefully note three leading forms, the feather-veined, the palmate-veined, and the triple-veined. The feather-veined (pinni-veined) leaf is that in which the venation consists of a midvein giving off at intervals lateral veinlets and branch- ing veinulets. Ex. beech, chestnut. 260. In the eadiatb-veined (palmi-veined) leaf the venation con- sists of sever
. Class-book of botany : being outlines of the structure, physiology and classification of plants : with a flora of the United States and Canada . Botany; Botany; Botany. 64 FOEM OB FIGUBB. 269. Of the reticulate venation, the student should carefully note three leading forms, the feather-veined, the palmate-veined, and the triple-veined. The feather-veined (pinni-veined) leaf is that in which the venation consists of a midvein giving off at intervals lateral veinlets and branch- ing veinulets. Ex. beech, chestnut. 260. In the eadiatb-veined (palmi-veined) leaf the venation con- sists of several veins of nearly equal size, radiating from the base towards the circumference, each with its own system of veinlets. Ex. maple, crow-foot. 261. The tmpli-veinkd seems to be a form intermediate between the two others when the lowest pair of veinlets are conspicuously stronger than the others above them towards the apex, extending with the midvein towards the summit. 262. In paeallkl-veined venation the veins are either straight, as in the linear leaf of the grasses, curved, as in the oval leaf of the orchis, or transverse as in the Canna, Calla, <fec. FOKM OR FIGUEE. U4. no 118 Forms of leaves. 110, Ehododendron maximum. HI, Alnus glutinoaa (cult). 112, Poly- gonam sagittatum. â 118, Pawpaw. 114, Impatlens fulva. 115, Coltis Americana. 116, Circaea Lutetiana. 117, Catmint. 113, Solidago Canadensisâa triple-veined leaf. 263. That infinite variety of beautiful and graceful forms for which the leaf is distinguished heoomes intelligible to the student only when viewed in connection with its venation. Since it is through the veins alone that nutriment is conveyed for the development and extension of the parenchyma, it 'follows that there will Be the greatest extension of oaiUne when tho veins are largest and most numerous. Consequently the form of the leaf will depend upon the direction of the veins and the vigor of their action in developing the intervening tissue. In our de
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