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and show successful growth. On the other 

 hand, a variety that has grown for years in 

 a wet climate exhibits modifications of the 

 leaf tissue, and develops a different type 

 of stoma, and if the variety, so modified, 

 be moved to a dry district, it seems to be 

 incapable of placing itself sufficiently quickly 

 in harmony with the new environment to 

 show immediately vigorous growth, though 

 this may come with years of adaptation. 

 On the contrary, it continues to transpire 

 large quantities of water, which, though 

 not excessive where supplies are abundant, 

 must be so designated where supplies are 

 restricted. 



Sometimes a farmer is forced to purchase 

 seed, by reason of the fact that his home- 

 grown supplies are much contaminated by 

 impurities. On some farms, for instance, 

 wild oats are so abundant that home-grown 

 grain cannot be used as seed. 



The case of seed potatoes is not quite 

 on all-fours with those just indicated, because 

 the potato crop, as the term is ordinarily 

 used, is not grown from seed but from 

 cuttings ; propagation, in the agricultural 

 and horticultural sense, being directly com- 

 parable with the raising of poplars, willows, 

 gooseberries, and currants, from cuttings, 



H 2 



