CHAPTER XXXI 



PARENT AND OFFSPRING 



317. Which plants and animals are to live. A casual ob- 

 server, when looking at a forest, would say that many of the 

 ___^_____^^____________ i trees are alike. As soon 



as he looks closely and 

 attempts to find two that 

 are exactly alike, he finds 

 himself in difficulty. It 

 is exceedingly doubtful 

 if any forest, however 

 large, contains two trees 

 which are exactly alike. 

 It will be instructive to 

 try to find two exactly 

 like objects of the same 

 kind, as leaves of an oak 

 or maple tree, pebbles on 

 the shore of a lake or bank 

 of a stream, or chickens or 

 pigs in a barnyard. 



While we should have 

 difficulty in finding like 

 objects of the same kind, 

 we should rarely fail to 

 recognize the relationship 

 of the same kind of objects. 

 We can recognize oak 



differences in characters of the heads. The trees, and most people Can 

 number of inferior heads is so great that distinguish between red 

 the yield would be small. Photograph by 



R M. Mead oaks, white oaks, black 



2SK) 



FIG. 133. Variation in wheat 



These heads are taken from wheat that was 

 grown by the Pima Indians. Note the wide 



