OF THK VEINS. 



53 



apex, as seen in the leaf of the 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, 

 five-veined, etc. Jix. 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. 



loa 



109 



Tarieties of venation. 106, feather-veined, — ieaf of Betulapopulifolia (wliitc birch), lying upon 

 a leaf of plum-tree ; same venation ^vith different outlines. 107, Palmate-veinerl. — leaf of white 

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

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

 (Lygodium). 



258. Modes op venation. Botanists distinguish three principa. 

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

 grand divisions of the vegetable kingdom already noticed. 



Reticulate, ob 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 kind of irregular net-work. 



Parallel-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. 



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

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

 manner, and do not re-unite. 



