190 



ELEMENTARY STUDIES IN BOTANY 



The pinnate and palmate leaves are often called net- 

 veined leaves, to distinguish them from the parallel-veined 

 leaves, but really they are all net-veined leaves, the dif- 

 ference being that in pinnate and palmate leaves the network 

 of veins is visible, while in parallel-veined leaves it is invisible. 

 It is a common statement that Dicotyledons have pinnate 

 and palmate leaves, while Monocotyledons have parallel- 

 veined leaves. This 

 is generally true of 

 Angiosperms that 

 grow in temperate re- 

 gions, but when tropi- 

 cal plants are included, 

 the distinction van- 

 ishes, for the banana 

 has good pinnate 

 leaves and the palm 

 leaf used for " palm 

 leaf fans" is palmate, 

 and both of these 

 plants are Monocoty- 

 ledons. The real leaf 

 distinction between 

 Monocotyledons and 

 Dicotyledons is that 

 in Dicotyledons the veinlets end freely in the margin of the 

 leaf (as well as elsewhere), forming an " open system " of 

 veins' (Fig. 155) ; while in Monocotyledons the veinlets do 

 not end freely, but are all part of a "closed system." 



One of the notable differences among leaves is that the 

 margins of some of them are variously toothed or lobed, 

 while in others they are not. In the latter case the leaf is- 

 said to be entire (Fig. 154, A and C). Leaves with a closed 

 system of veins are always entire, which means that most of 

 the Monocotyledons have entire leaves. Leaves with an 



FIG. 156. Compound (branching) leaves: A, pin- 

 nately compound leaf of black locust ; B, pal- 

 mately compound leaf of red clover. 



