102 Elementary Species 



the races is a condition implanted in them by 

 man, and nature always strives against this 

 arbitrary and one-sided improvement. Numer- 

 ous slight differences in characters and numer- 

 ous external influences benefit the minor types 

 and bring them into competition with the better 

 ones. Sometimes they tend to supplant the 

 latter wholly, but ordinarily sooner or later a 

 state of equilibrium is reached, in which hence- 

 forth the different sorts may live together. 

 Some are favored by warm and others by cool 

 summers, some are injured by hard winters, 

 while others thrive then and are therefore rela- 

 tively at an advantage. The mixed condition 

 is the rule, purity is the exception. 



Different sorts of cereals are not always 

 easily distinguishable by the layman and there- 

 fore I will draw your attention to conditions in 

 meadows, where a corresponding phenomenon 

 can be observed in a much simpler way. 



Only artificial pasture-grounds are seen to 

 consist of a single species of grass or clover. 

 The natural condition in meadows is the occur- 

 rence of clumps of grasses and some clovers, 

 mixed up with perhaps twenty or more species 

 of other genera and families. The numerical 

 proportion of these constituents is of great in- 

 terest, and has been studied at Eothamstead in 

 England and on a number of other farms. It is 



