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Selection of Elementary Species 101 



Europe from whence it has been introduced in 

 the United States. In summers which are un- 

 favorable to the development of the cultivated 

 oats it may be observed to multiply with an al- 

 most incredible rapidity. It does not contrib- 

 ute to the harvest, and is quite useless. If no 

 selection were made, or if selection were dis- 

 continued, it would readily supplant the culti- 

 vated varieties. 



From these several observations and experi- 

 ments, it may be seen, that it is not at all easy 

 to keep the common varieties of cereals pure 

 and that even the best are subject to the en- 

 croachment of impurities. Hence it is only 

 natural that races of cereals, when cultivated 

 without the utmost care, or even when selected 

 without an exact knowledge of their single con- 

 stituents, are always observed to be more or 

 less in a mixed condition. Here, as everywhere 

 with cultivated and wild plants, the systematic 

 species consist of a number of minor types, 

 which pertain to different countries and cli- 

 mates, and are growing together in the same 

 climate and under the same external conditions. 

 They do not mingle, nor are their differentiat- 

 ing characters destroyed by intercrossing. 

 They each remain pure, and may be isolated 

 whenever and wherever the desirability for 

 such a proceeding should arise. The purity of 



