PLANT BREEDING 



359 



same genus (including the eggplant and the nightshades) 

 came in turn from a single still older species. But one 

 difference is worth noting between the varieties that have 

 developed among wild plants and 

 those that have been produced by 

 breeding. No variety can exist for 

 any length of time in the wild state 

 unless it is particularly well fitted to 

 the conditions about it, and especially 

 unless it has very effective means of 

 reproduction. But there are many 

 varieties of cultivated plants which 

 would be quite unable to live, or to 

 reproduce, or both, if they were not 

 carefully cultivated and propagated 

 by artificial means. We do not 

 know, for example, what the original 

 ancestor of the Indian corn may 

 have been ; but none of its present- 

 day varieties thrives except in culti- 

 vation. If some corn plants do 

 spring up in a wild state, their de- 

 scendants die out in the course of 

 two or three generations at most, 

 largely because they have no way of 

 distributing their heavy fruits. 



The wild ancestors of our culti- 

 vated plants were in almost all cases 

 much less useful or attractive to man 

 than their cultivated descendants 

 are. The original plants must, how- 

 ever, have had some valuable qualities, or men would not have 

 begun to cultivate them. After the cultivation of a particu- 

 lar species began, it was noticed that some individual plants 

 of the species were better adapted than others to the purpose 



FIG. 202. The result 

 of seven years of breeding. 

 The head of barley on the 

 right is one of a variety 

 developed from one repre- 

 sented by the head at the 

 left. 



