ON THE STONELESS PLUMS AND PRUNES 



the method through which the stoneless plums of 

 various kinds, including the prune, were devel- 

 oped. It seems desirable, however, to examine at 

 some length the relations that obtain between the 

 stony seed-covering and the general and especial 

 needs of the plant; and to correlate this type of 

 seed covering with other types of protective seed- 

 covering that serve the same or a similar function 

 in the case of other tribes of plants. 



When man takes a plant under his care, some 

 of its many parts may become of little use, because 

 of the changed conditions of the artificial environ- 

 ment. 



Thus the wild oat has a pointed, saw-like 

 beard, which, turning and twisting under influence 

 of moisture and heat, helps the seed to burrow into 

 the earth. This is obviously useful to the plant in 

 a state of nature. But it becomes a useless piece 

 of baggage when the plant has been tamed and 

 grown by man, for man will see that the seed is 

 planted, in return for the crop it yields. 



The blackberry, domesticated, has no further 

 use for the thorny armor that was originally de- 

 veloped to protect it from destruction by animals 

 that would browse on its leaves and stems or 

 trample it to death. 



In the same way the cactus, when taken under 

 cultivation, can dispense with the spines that were 



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