DEVELOPMENT OF LEAVES AND STIPULES 59 



pairs of lateral nerves in the upper half of the leaf and 

 eighteen in the lower. In the perfect leaf, on the 

 contrary, each half bears thirteen. 



In some cases, however, the growth of the leaf as a 

 whole and that of the separate leaflets follows different 

 lines. 



Trecul, moreover, has shown that the development 

 of leaves cannot in all cases be brought under these two 

 categories. In Oentaurea, for instance (fig. 99), the 

 central lobe is formed first, and 

 others appear successively, both up- 

 wards and downwards. 



There has been much difference 

 of opinion whether any, and, if so, 

 what, other modes of development 

 exist in addition to those already 



mentioned, but from my special LEAP OP CENTAUREA 



. . f, . . . SCABIOSA, x 14. The 



point of View it IS not necessary to larger leaf embraces 



go into this question. 



FIG. 99. YOUNG 



a younger one at its 



GALIUM 



The following figures, after Eichler, illustrate the 

 development of the leaf in the Ladies' Bedstraw 

 (Galium Mottuyo). Fig. 100 gives a vertical view of the 

 tip of a shoot. Round the central growing-point is 

 a nearly circular ridge. Immediately below this is 

 another ridge, which shows a number of small emi- 

 nences two larger, right and left, which are the rudi- 



