OF THE VEINS. 



63 



apex, as seen in the leaf of tlie oak or birch. If there be several simi- 

 lar divisions of the petiole, radiating from the base of the leaf, they are 

 appropriately termed veins ; and the leaf is said to be three-veined, 

 flve-veined, etc. Ex. maple. 



257. The primary branches sent off from the midvein, or the veins 

 we may term the veinlets, and the secondary branches, or those sent 

 off from the veinlets, are the veinulets. These also branch and subdi- 

 vide until they become too small for vision. 



lOT 



loe _ 109 



Varieties of venation. 106, featlier- veined, — ^leaf of Eetulapopulifolia (white bircli), lying: upon 

 aleaf of plum-tree; same venation with different outlines. lOT, Palmate-veined. — leaf of white 

 maple, contrasted with leaf of Circis Canadensis. 108, Parallel venation, — plant of "three-lo.ived 

 Solomon's-seal," (Asteranthemum trifoliatum Kunih.) 109, Forked venation, — climbing fern 

 (Lygodium), 



258. Modes of venation. Botanists distinguish three principa. 

 modes of venation, which are in general characteristic of the three 

 grand divisions of the vegetable kingdom already noticed. 



Eeticulate, or net- veined, as in the Exogens : this kind of vena- 

 tion is characterized by the frequent reunion' or inosculation of its nu- 

 merously branching veins, so as to form a kij^d of irregular net- work. 



Paeallel-veined, as in the Endogens. The veins, whether straight 

 or curved,' run parallel, or side by side, to the apex of the leaf, or to the 

 margin, and are always connected by simple transverse veinlets. 



Foek-veined, as in the ferns (and other Cryptogamia, where veins 

 are present at all). Here the veins divide and subdivide in a furcate 

 manner, and do not re-unite. 



