106 Elementary Species 



ical culture of cereals of his time. In his poem 

 Georgics (I. 197) the following lines are found: 



Vidi lecta diu, et multo spectata labore 

 Degenerare tamen, ni vis humana quotannis 

 Maxima quaeque manu legeret. 

 (The chosen seed, through years and labor 



improved, 



Was seen to run back, unless yearly 

 Man selected by hand the largest and fullest 

 of ears.) 



Elsewhere Virgil and also some lines of 

 Columella and Varro go to prove in the same 

 way that selection was applied by the Eomans 

 to their cereals, and that it was absolutely 

 necessary to keep their races pure. There is 

 little doubt, but that it was the same principle 

 as that which has led, after many centuries, to 

 the complete isolation and improvement of the 

 very best races of the mixed varieties. It fur- 

 ther proves that the mixed conditions of the 

 cereals was known to man at that time, al- 

 though distinct ideas of specific marks and dif- 

 ferences were of course still wholly lacking. It 

 is proof also that cultivated cereals from the 

 earliest times must have been built up of num- 

 erous elementary forms. Moreover it is very 

 probable, that in the lapse of centuries a good- 

 ly number of such types must have disap 



