SUMMAKY 227 



9. Sometimes they act as reserves of nourishment, 

 as in Gunnera. 



10. Sometimes they serve for a support to the stem, 

 as in some species of Polygonum. 



The view here suggested seems to apply well both 

 to the cases where the stipules are very short-lived, 

 and also to those in which they are very persistent. 

 When they serve, and serve only, to protect the leaves 

 to which they themselves belong, they often fall off 

 when the leaves themselves expand. On the other 

 hand, as a general rule, they protect the following leaf 

 or leaves, as, for instance, in Magnolia, Liriodendron, 

 and other Magnoliacece. When the stipules of the 

 'terminal leaves of one year protect the next leaves, 

 which do not emerge till the following year, they are 

 much more persistent than the leaves themselves. Both 

 cases sometimes occur in the same family. 



This, then, is the answer I should give to M. 

 Vaucher's question (see p. 20), and the presence or 

 absence of stipules is not determined, I think, as sug- 

 gested by De Candolle, by any question of general 

 symmetry, but rather by practical considerations con- 

 nected with the wants and requirements of the plants. 



No doubt, also, there are some cases in which stipules 

 have ceased to be of any use to the plants, and are 

 merely the persistent rudiments of organs which per- 

 formed a useful purpose to the ancestors of the existing 



Q2 



