FORMS OF LEAVES. 



ribs, from along which branches lead off dividing and subdividing several 

 times, and then finally anastomosing so as to form literally a net-work 

 of veins; whence the name of this kind of venation. (Figs. 19 and 41.) 



29. When there is a single main rib running through the center of the 

 leaf from base to apex, and sending off branches from each side like the 

 vanes of a feather, it is said to be feather-veined OY p innately veined (from 

 L. pinna, a feather.) These leaves are usually longer than broad. 

 (Figs. 4 and 19.) 



30. When there are several main ribs radiating from the summit of 

 the petiole through the substance of the leaf, and these in turn sending 

 out their branches, the leaf is said to be from that fact radiate-veined or 

 palmately (from L. palma, the hand) or digitately (from L. digitus, the 

 finger) veined, from resemblance to the hand, witli fingers spread apart. 

 (Fig. 5.) Leaves of this type are broader in proportion to length than 

 the pinnately veined-. Contrasted with the netted- 



veined leaves are the 



31. Parallel-veined, where the veins commence at 

 the base of the leaf, and run approximately parallel 

 to the summit, where they again unite, and only 

 minute simple cross-veinlets, if any, are given off. 

 Leaves of this sort are seen in Grasses, Wheat, 

 Indian Corn, Solomon's Seal, etc. A modification of 

 this kind of venation is seen in the Calla, Banana, etc., 

 where the veins run out transversely to the margins. 



32. The plants having parallel veined leaves com- 

 prise a large and important .class, but in temperate 

 climates they are nearly all herbaceous and not for 

 our consideration here. 



FIG. 5. 



33. The Forms of Leaves are intimately connected with the vena- 

 tion. They are very various, but as a rule quite constant within the 

 same species, and consequently form an important item in the classifica- 

 tion of plants. 



34. We need to consider especially the elongated types as most com- 

 monly seen associated with the pinnate venation. To get the best idea 

 of the forms of these leaves, we might group them as follows: (1) those 

 of about uniform width; (2) those broadest near the base; (3) at about 

 the center, and (4) near the apex. Taking them in this order a leaf is 

 said to be 



Linear, when the sides are parallel, 

 i. e., when it is of uniform width, and 

 is several or many times longer than 

 broad. (Fig. 6.) 



Oblong, when of uniform width, but 

 only two or three times as long as 

 broad. (Fig. 7.) 



Lanceolate, when broadest at the 

 base, and tapering to the apex or both 

 Linear. Obiong. Lanceolate, ways, and is four or five times or more 



FIG. 6. FIG. 7. FIG. 8. longer than broad. (Fig. 8.) 



Fig. 5. A Palmately-veined Leaf. 



