VEINING 



35 



in the last, the petiole seems to be continued in a large 

 central vein, called the Midrib, from 

 which the secondary veins branch off 



on either side just 



as the pinnae of a 



feather do from the 



quill ; whence such 



leaves are said to be 



pinnately, or feather 



veined. In the cot- 

 ton, maple, ivy, etc., 



on the other hand, 



the petiole breaks up 



at the base of the leaf (Fig. 55) into a 

 number of primary veins or ribs, which radiate in all direc- 

 tions like the fingers from the palm of the hand ; hence, 

 such a leaf is said to be palmately veined. 



57. — Pinnately net- 

 veined leaf of awillow. 



56. — Pinnately paral- 

 lel-veined leaf of cala lily 

 {after GRAY). 



39. Ribbed Leaves. — Net-veined leaves are sometimes 

 ribbed in a way that might lead an inexperienced observer 

 to confound them with parallel-veined 

 ones. Compare, for instance, a leaf of 

 the wild smilax (often improperly called 

 bamboo), or of the common plantain, with 

 one of the kind represented in Figure 54. 

 A little inspection will show that in both 

 the ribs all proceed from the same point 

 at the top of the petiole, as in other 

 leaves of the palmate kind, of which they 

 are varieties, but the reticulations between 

 the ribs in the smilax and plantain show 

 that they belong to the net-veined division. ^ ' 



Ribbed leaf of 

 plantain. 



40. Parallel-veined and Straight-veined Leaves. — In 



some pinnate leaves, like the elm, beech, birch, dogwood, 

 etc., the secondary veins are so straight and regular that 

 beginners are apt to confound them with the parallel kind 

 represented in Figure 56, but this mistake need never occur 



