THE LEAVES OF VASCULAR PLANTS. 251 



are two ; those of Oxalis tetraphylla, where there are 

 four, &c. But we will revert to this subject after we 

 have examined compound leaves. 



If the position of a pahnate leaf which corresponds to 

 each partial nerve be examined, we shall see that this 

 nerve emits lateral ones, in the manner of penninerved 

 leaves, and all that we have said above is appKcable to 

 them ; whence it resiilts that a palminerved leaf may be 

 considered as formed of as many penninerved leaflets, 

 united at the base, as there are principal nerves ; and it is 

 particularly favourable to this opinion, that the families 

 which have palminerved leaves present also compound 

 ones, formed in an analogous manner ; such as the Am- 

 pelideae, Malvaceae, &c. This opinion will be still better 

 understood, when, on studying compound leaves, it is 

 remarked that all leaflets, even those of palmate leaves, 

 are penninerved. 



The general form of palminerved leaves is essentially 

 determined by the degree of divergence of the principal 

 nerves, by their relative length, and by their number. 

 When they are not numerous and but slightly diverging, 

 the leaf may have a narrow and long form : it will, on 

 the contrary, be wider or rovmder as the nerves are 

 more numerous and more diverging. The extreme case 

 of this last combination is that which constitutes the 

 third class of leaves — that of peltinerved ones. 



3d. Leaves are said to be Peltinerved, and the 

 nerves Peltate, when from the summit of the petiole 

 there spring several nerves which radiate upon the same 

 plane, which is not in the direction of the petiole, but 

 forms with it an angle, often a right one, or nearly so, 

 and the two external nerves are so near that the lateral 

 limb of each is joined to the other. It results from 

 this disposition, that in this kind of leaf the limb does 

 not seem to be the prolongation of the petiole, but has 



