112 



ELEMENTS OF STBUCTUEAL BOTANY. 



is in three separate pieces, each of which is called a 

 leaflet, but alLof which, taken collectively, constitute the 

 blade of the leaf. The leaf of the Mallow is simple ; 

 that of the Clover is compound. Between the simple 

 •and the compound form there is every possible shade of 

 gradation. In the Mallow leaf the lohes are not very 

 clearly defined. In the Maple (Fig. 143) they are well 



Fig. 141. "W Kg. 142. 



marked. In other cases, again, the lobes are so nearly 

 sepirate that the leaves appear at first sight to be really 

 compound. 



168. You will remember that in our examinations of 

 dicotyledpnous plants, we found the leaves to be invariably 

 net- veined. But, though they have this general character 

 in common, they differ considerably in the details of 

 their veining, or venation, as it is called. The two 

 leaves employed as illustrations in the last section will 



Fig. 141.— Simplei)almatcly-veined leaf of Mallow. 

 Fig. 142.— Compound leaf of Clover. 



