102 



BOTANY AND PHARMACOGNOSY. 



the work of assimilation, as in the case of certain green stems. 

 Then again there are cases in ^(vhich the leaves are reduced, and 

 the work of assimilation is cai-ri^d on exclusively by the shoot- 



FiG. 66. Bryonia dioica. a, young, spirally coiled tendril; b, expanded and irritable 

 tendril; c, tendril which has grasped a support; d, tendril which has not grasped a support, 

 and has undergone the old-age coiling. — After Pfeffer. 



axes, as, in most Cactacese, certain marsh-plants and others, On 

 the other hand the shqot-axis may be modified so a§ to increase the 

 assimilating surface, as by a flattening of the axis, as in some of 



