VEINS. 85° 
- 223. The lamina is generally of a rounded oval outline, longer 
than wide, with equal sides but unequal ends. It is, however, 
subject to variety almost infinite in this respect. The end of 
the blade next the stem is the Jase, and that most remote, the 
apex. 
224. A leaf is simple when its blade consists of a single piece, 
however cut, cleft, or divided; and compound when it consists 
of several distinct blades, supported by as many branches of a 
compound petiole. 
225. The frame-work, or skeleton, of the lamina above men- 
tioned, consists of the ramifying vessels of the petiole, while the 
lamina itself is, of course, parenchyma (29). These vessels are 
collectively called vews, from the analogy of their functions. 
226. The manner in which the veins are divided and distrib- 
uted is termed venation. The organs of venation, differing from 
each other only in size and position, may be termed the midvein, 
veins, veinlets, and veinulets. (The old terms midrib and nerves, 
being anatomically absurd, are here discarded.) 
227. The mzdvein is the principal prolongation of the petiole, 
running directly through the lamina to the apex; as in the leaf 
of the birch. If there be several similar divisions of the petiole, 
radiating from the base of the leaf, they are appropriately 
termed the veins; and the leaf is said to be three-veined, five- 
veined, &c. Ex. maple. 
228. The primary branches sent off from the midvein or the 
veins we may term the vezn/ets ; and the secondary branches, or 
those sent off from the veinlets, are the veznulets. 
229. There are three principal modes of venation which are, in general, char- 
acteristic of the three grand divisions of the vegetable kingdom. 
Ist. Reticulate or net veined, as in Exogens. The petiole is 
prolonged into the leaf in the form of the midvein, or several pri- 
mary branches, dividing and subdividing into branchlets, which 
unite again, and by their frequent inosculations form a kind of 
network. . Ex. maple, bean. 
2nd. Parallel-veined, as in Endogens. In this kind of vena- 
tion the veins are all parallel, whether proceeding from the base 
of the leaf to the apex, or sent off laterally from the midvein,and 
