1 62 



Regeneration 



but when we isolate each notch leaving as much 

 of the rest of the leaf as possible attached to it, each 

 notch will give rise to a new plant. 1 (Fig. 17.) We 

 see, therefore, that it does not even require a whole 

 plant to cause inhibition but that we may observe the 

 tyranny of the whole over the parts in a single leaf. 



The explanation 

 is as follows : 

 When we isolate 

 a leaf, some of 

 the notches will 

 commence t o 

 grow into new 

 plants and this 

 growth will ar- 

 rest the develop- 



FIG. 17. If all the notches of a leaf are iso- , /. , , 



lated from each other each notch will give rise 



to roots and a shoot, but the growth will be other notches of 

 less rapid than in Fig. 16. Figs. 16 and 17 

 were two leaves taken from the same node 

 of a plant. 



their development was suppressed by the whole plant. 

 The explanation is the same; those notches which 

 begin to grow first will attract the flow of substances 

 to themselves, thus preventing the other notches from 

 getting those substances. This idea is supported by 

 the fact that if all the notches are isolated from the 

 leaf each notch will give rise to a slowly growing 

 1 Loeb, J., Bol, Gazette, 1915, lx., 249, 



the leaf in the 

 same way as 



