226 BUDS AND STIPULES 



The general function of stipules being to protect 

 the younger leaves, their presence or absence depends 

 in great measure on the need for such protection. 

 Hence we may almost lay it down as a general rule 

 that where the leaf-stalk is broad and covers the bud 

 there are no stipules, and that where it is too narrow 

 to protect the bud stipules are present. 



The protection of the bud is, indeed, the general 

 function of stipules, though by no means the only one. 

 We may summarise the uses of stipules as follows : 



1. To protect the bud. 



2. To help in performing, or even, as in Lathyrus 

 Aphaca, to perform, the function of leaves. 



3. Sometimes they are hardened into spines, and 

 thus serve to protect the whole plant, as in Robinia 

 (so-called Acacia). 



4. Sometimes they form hooks, and assist the plant 

 in climbing (Paliurus). 



5. Sometimes they are developed into tendrils, as in 

 Smilax. 



6. Sometimes they secrete gum, which helps to 

 protect the bud ; 



7. Or a sweet secretion, which attracts wasps, &c, 

 as in some species of Viburnum. 



8. Sometimes they serve to hold water, as, for 

 instance, in some species of Viola, Thalictrum and Poly- 

 gonum. 



