118 Elementary Species 



the compound nature of so-called species of 

 cultivated plants seems to be beyond all doubt, 

 and its practical importance is quite obvious. 



Acclimatization is another process, which is 

 largely dependent on the choice of adequate 

 varieties. This is shown on a large scale by 

 the slow and gradual dispersion of the varieties 

 of corn in this country. The largest types are 

 limited to temperate and subtropical regions, 

 while the varieties capable of cultivation in 

 more northern latitudes are smaller in size and 

 stature and require a smaller number of days 

 to reach their full development from seed to 

 seed. Northern varieties are small and short 

 lived, but the " Forty-day-corn " or " Quaran- 

 tino maize " is recorded to have existed in 

 tropical America at the time of Columbus. In 

 preference, or rather to the entire exclu- 

 sion of taller varieties, it has thriven on the 

 northern boundaries of the corn-growing states 

 of Europe since the very beginning of its culti- 

 vation. 



According to Naudin, the same rule prevails 

 with melons, cucumbers and gherkins, and other 

 instances could easily be given. 



Referring now to the inferences that may be 

 drawn from the experience of the breeders in 

 order to elucidate the natural processes, we will 

 return to the whitlow-grasses and pansies. 



