170 



BRITISH FLOWERING PLANTS 



and the older leaf (Fig. 119). Moreover, the function of 

 the stipule being to protect the young bud, it develops 

 early, and when it is full grown the lower limb is 

 equal in length to the internode below. Subsequently, 

 however, the internode becomes much longer, while the 

 stipule remains as before. But though the stipule may 



Fig. 116. Fig. 117. Fig. 118. Fig. 119. 



Pig. 116. — Stipule of Lathyrus Figs. 118, 119, — Stipules of Lathyrus lalifolivs. 



pratensis. \\ uat. size. Tlie lower stipule {st) has 



Fig. 117. — One of the lower been removed in Fig. 119, exposing the 



stipules is turned back ex- whole of the stipule {st') of the next higher 



posing the next younger leaf leaf. 



with its stipules. 



be correctly described as half sagittate, it sometimes 

 shows a minute tooth where the other barb would have 

 been, suggesting that it is descended from ancestors 

 which had a barb on each side. 



In L. pratensis the stipules (Figs. 115-117) are 

 sagittate. Here, however, the petiole is round ; the 

 wings lie one on each side of it (Figs. 116, 117), and 

 are fully covered by the stipule of the preceding leaf 

 Thus, then, the diiference between the sagittate and 



