232 ARID AGRICULTURE. 



rather than to any inherent qualities in the plants 

 themselves. It is true that artificial selection 

 was carried on by Roman farmers, perhaps as 

 early as the beginning of the Christian era. Vir- 

 gil, in his poem Georgics (1-197), as translated 

 by DeVries, says : 



"The chosen seed through years and labor im- 

 proved,, 



Was seen to run back, unless yearly 

 Man selected by hand the largest and fullest of 



He says further, "elsewhere Virgil, and some 

 lines of Columella and Varro, go to prove in the 

 same way that selection was applied by the Ro- 

 mans to their cereals, and that it was absolutely 

 necessary to keep their races pure.' 7 DeVries 

 goes on to show how nearly all crops were then, 

 as they are now, composed of mixed varieties, 

 The mixed condition was known, but men had no 

 distinct ideas of either specific marks or variety 

 differences, and many of the elementary forms 

 have entirely disappeared. Bailey states that 

 there are one hundred cultivated varieties of 

 plants, the primitive ancestors of which cannot 

 be certainly traced. This is a large per cent, 

 of the whole, as DeCandolle recognizes but two 

 hundred and forty-eight cultivated species. 



