54 



FORM OR FIGURE. 



259. 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-veincd) leaf is that in |jhich the venation 

 consists of a midvein giving off at intervals lateral veinlets and branch- 

 ing veinulets. Ex. beech, chestnut 



260. In the badiate-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 tkipli-veined seems to bo a forni intermediate betwe(^n 

 the two others when the lowest pair of veinlets are -conspicuously 

 stronger than the others above them towards the apex, extending witti 

 the midvein towards the summit. 



262. In paballbl-veined venation the veins arc either straight, n& 

 in the linear leaf of the grasses, curved, as in the oval leaf of the 

 orchis, or tra7isvcrse as in the Canna, Calla, &o. 



B'ORM OR FIGURE. 

 114 



110 118 



Forms of leaves. 110, Ehododendron maximum. Ill, Alnus glutiiiosa (cult.). 112, Poly- 

 gonum Bagittatum. 113, Pawpaw, 114, Impatiens fulva. 115. Celtis Americana. 116, Circap.a 

 Lutotiana. 117, Catmint IIS, Solidago Canadensis — a triple-veined leaf. 



263. That infinite variety of beautiful and graceful forma for which the loaf 1b 

 distinguished becomes 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 tli.at there will be 

 the greatest extension of ouilins when the 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 intei'veiiing tissue. In our description 



