284 VEGETABLE ORGANOGRAPHY. 



processes of the coussinet ; 2d, that when the coussinet 

 has a tendency thus to be prolonged into a spine, the 

 stipules which ought to spring above it are frequently 

 abortive. 



Lastly, stipules may appear to be, like certain petioles, 

 capable of being transformed into tendrils : it is perhaps 

 a transformation of this kind which gives origin to the 

 tendrils of the Cucurbitaceae ; we see in following the 

 vegetation of Tra2)a natans, that those stipules which 

 grow under water are elongated, and not unlike simple 

 tendrils, whilst those which are produced in the air are 

 flat, oblong, and resembling for the most part ordinary 

 stipules. 



The size of stipules, though less variable than their 

 texture, also presents remarkable differences ; in general 

 they are smaller than the leaves, but there are some 

 plants in which the stipules are developed more than the 

 true leaves, and then they perform the physiological 

 functions of these organs ; this happens very evidently in 

 Lathjrns aphaca, where the leaflets are almost always 

 abortive, and the stipules alone elaborate the sap. The 

 contrary takes place in several other Leguminosae, where 

 the stipules are so small that it may be said that they 

 are almost completely absent, and frequently even they 

 are absolutely abortive. 



The duration of stipules is also one of the variable 

 modifications of this organ ; there are some which are 

 persistent at the base of leaves throughout their exist- 

 ence, and fall off nearly at the same time with them ; 

 these are generally those of a foliaceous texture, which 

 follow thus the lot of the leaves. There are others, 

 principally membranous ones, which fall off very early, 

 such are those of the Oak and most Amentaceae ; this 

 circumstance often makes us fancy that they are wanting 

 where they have simply dropped off early ; lastly, there 



