186 GENERAL BOTANY 



is really the continuation of the main axis, the apparent 

 continuation being the axillary branch of that leaf 

 a case of sympodial growth. 



In most cases the tendril is to be considered a 

 modified leaf or part of a leaf, or leaflet. 



In various species of BIGNONIA (fig. 23), this is 

 easily seen to be the case, the leaf consisting obviously 

 of two leaflets and a tendril. Occasionally, one may 

 find one or more of the branches of the tendril expanded 

 into blades, that is, reverted into leaflets. 



In PISUM, the common Pea, the whole of the leaf is 

 modified into a branched tendril, the branches corre- 

 sponding to leaflets, and the functions of the leaf are 

 undertaken by the very large stipules. 



In GLORIA SUPERBA (fig. 22] the tip of the leaf is 

 prolonged as a tendril. 



In SMILAX outgrowths from the base of the leaf 

 act as tendrils. These are sometimes said to be 

 modified stipules, but as no others of the plants of 

 that family possess stipules, it is better to consider 

 them as special tendrilar outgrowths of the leaf-base. 



In CUCUMis, the Melon, Cucumber, etc. and other 

 CUCURBlTACE^i, the tendril is partly a branch partly 

 a leaf structure. 



Emergencies 



So far we have been studying plants with thorns,, 

 spines or other structure which by observation of their 

 position and surroundings we must consider to be modi- 

 fied branches, stipules or parts of leaves. But there are 

 many plants with structures to which we cannot assign 

 in the same way the same morphological importance. 



