PRACTICAL POLLIXATIOX 247 



and evolution for these large-growing plants in 

 penalty for their renunciation of the services of 

 insect messengers. 



The case of the trees, then, simply illustrates 

 the fact that there may be more than one way 

 to effect a given purpose, and that a change of 

 method may be no barrier to progress, even 

 though the abandoned method still remains an 

 admirable one for a vast coterie of organisms of 

 slightly diiferent habit. 



Self-Feetilized Plants 



But the case of the other company of plants 

 that have backslidden from the insect alliance 

 is altogether different. 



The plants in question do not make up any 

 great conspicuous tribe comparable to the forest 

 trees, but are a miscellaneous company of lowly 

 vegetables of unrelated families. Familiar ex- 

 amples are the wheat of the fields, peas and beans 

 in our garden, and a certain number of the more 

 obscure species of violets. 



The jewel weed, the fennel, the rue, and the 

 nettle are other somewhat less familiar yet not 

 uncommon tribes of plants whose flowers are 

 habitually self-fertilized. 



There can be no question that these plants are 

 the descendants of tribes that were at one time 



