178 



BUDS AND STIPULES 



if the upper stipule had a lower limb on the outer side, 

 the latter would be exposed. The lower limb, which is 

 on the inner side, lies snugly ensconced between the 

 stem and the older leaf (fig. 301). Moreover, the func- 

 tion of the stipule being to pro- 

 tect the young bud, it develops 

 early, and when it is full-grown 

 the lower limb (fig. 301) is equal 

 in length to the internode below. 

 Subsequently, however, the in- 

 ternode becomes much longer, 

 while the stipule remains as be- 

 fore. But though the stipule may 

 be correctly described as half- 

 sagittate, it sometimes (see fig. 

 298) shows a minute tooth where 

 the other barb would have been, 

 indicating that it is descended 

 from ancestors which had a barb 

 on each side. 



In L. pratensis the stipules 



Fig. 302. 



Fig. 303. 



Stipules of Lathyruspkatkx- (fi 302) are sagittate. Here, 

 sis. One-and-a-half nat. size. v ' 



in fig. 303 one of the lower stipules however, the petiole is round ; 



is turned back, exposing the next 



younger leaf with its stipules. the wings lie one on each side 

 of it (fig. 303), and are fully covered by the stipule of 

 the preceding leaf. 



Thus, then, the difference between the sagittate and 

 semi-sagittate stipules appears to depend on the form 



