v.l ORIGIN OF TENDRILS 49 



has succeeded experimentally in converting a leaf 

 into a tendril, the origin of them is obviously, 

 inductively considered, the result of the respon- 

 siveness of the protoplasm to mechanical irrita- 

 tions. Darwin shows how both form and 

 sensitiveness of the peduncle of a flowering 

 branch of the vine become more and more 

 of the nature of a true tendril in proportion 

 as the number of buds decreases, and vice 

 versa. " The gradations," he says, " from the 

 ordinary state of a flower stalk to that of a 

 true tendril is complete." l Sometimes the 

 tendril, which arises from the same stalk as 

 the bunch of grapes, becomes a duplicate one. 

 A "double cluster" is then produced. 



Now, as all these changes may go on in 

 the same vine, one cannot see what natural 

 selection has to do with the evolution either 

 of a bunch of grapes or a tendril. But, once 

 recognise both the origin of function and of 

 structure to be due to the inherent responsive- 

 ness of the protoplasm and nucleus, then every- 

 thing is at once explained. 



1 " Climbing Plants/' p. 141. 



G 



