134 



FOtnSTDATIONS OF BOTANY 



142. The Maple Leaf. — Sketcli the leafy twig. 

 Are the leaves arranged in rows like those of the elm. ? How are 

 they arranged? 



How are the petioles distorted from their natural positions to 

 bring the proper surface of the leaf upward toward the light ? 



Do the edges of these leaves show larger spaces between them 

 than the elm leaves did, i.e., would a spray of maple intercept the 

 sunlight more or less perfectly than a spray of 

 elm ? Pull off a single leaf and sketch its lower 

 surface, about natural size. 



Of the two main parts whose names have 

 already been learned (blade and petiole), which 

 is more developed in the maple than in the 

 elm leaf? 

 Describe : 



(a) The shape of the maple leaf as a whole. 

 To settle this, place the leaf on paper, mark the 

 positions of the extreme points and connect 

 these by a smooth line. 



(6) Its outline as to main divisions : of what 

 kind and how many. 



(c) The detailed outline of the margin 

 (Fig. 93). 



Compare the mode of veining or venation of 



the elm and the maple leaf by making a 



diagram of each. 



These leaves agree in being netted-veined ; i.e., in having veinlets 



that join each other at many angles, so as to form a sort of delicate 



lace-work, like Figs. 94 and 95. 



They differ, however, in the arrangement of the principal veins. Such 



a leaf as that of the elm is said to be feather-veined, orpinnately veined. 



The maple leaf, or any leaf with closely similar venation, is said to 



be palmately veined. Describe the difference between the two plans 



of venation. 



Fio. 96.— Plnnately 

 Divided Leaf of 

 Celandine. 



The blade of the leaf is 

 discontinuous, con- 

 sisting of several por- 

 tions between wMob 

 are spaces in which 

 one part of the blade 

 haa been developed. 



143. Relation of Venation to Shape of Leaves. — As soon 

 as the student begins to observe leaves somewhat widely, 



