104 Plant-Breeding 



there are definite records to show that such is often the 

 case. In fact, much of the rapid improvement in fruits 

 and vegetables in recent years is probably due to the 

 practice of buying plants and seeds so largely of dealers, 

 by means of which the stock is often changed. Even 

 a slight change, as between farms or neighboring villages, 

 sometimes produces marked results, such as more vigorous 

 plants and often more fruitful ones. We must not sup- 

 pose, however, that because a small change gives a good 

 result, a violent or very pronounced change gives a better 

 one. There are many facts on record to show that 

 great changes often profoundly influence plants, and when 

 such influence results in lessened vigor or lessened pro- 

 ductiveness, we call it an injurious one. Now, this in- 

 jurious influence may result even when all the condi- 

 tions in the new place are favorable to the health and 

 development of the plant; it is an influence wholly in- 

 dependent, as far as we can see, of any condition which 

 interferes injuriously with the simple processes of growth. 

 Seeds of a native physalis, or husk-tomato, were sent from 

 Paraguay in 1889 by Dr. Thomas Morong, then traveling 

 in that country. It was grown from cuttings in the house 

 and out of doors, and for two generations it failed to set 

 fruit, even though the flowers were hand pollinated ; yet the 

 plants were healthy and grew vigorously. The third cut- 

 ting-generation grown out of doors set freely. This is an 

 instance of the fact that very great changes of conditions 

 may injuriously affect the plant, and an equally good 

 illustration of the power to overcome these conditions. 

 Now there is great similarity between the effects of slight 

 and violent changes of conditions and small and violent 



