LOOSESTRIFE AND PIMPERNEL. 133 



under the altered conditions of its life. And, 

 finally, it (or some similar form) has further 

 developed the bog pimpernel and half a 

 dozen other more separate species, as well as 

 the still further differentiated chaffweeds, 

 which depart progressively more and more 

 widely from the common loosestrife pattern. 



The fact is, fruits and seeds are naturally 

 in one way the worst of all possible guides to 

 relationship by descent ; because, though 

 close likeness in fruits affords a fair presump- 

 tion of close kinship, unlikeness in fruits 

 affords no valid presumption against it. Two 

 plants may remain alike in their leaves, their 

 stems, their buds, and their flowers, and yet 

 when it comes to their fruit, new agencies 

 may be brought to bear upon them which for 

 the first time set up a slight difference 

 between them. This difference may often 

 be very conspicuous, and yet may be of ex- 

 tremely little genealogical importance. Thus 

 the almond and the nectarine are really so 

 much alike in all general points of structure 



