34 BOARD OF AGRICULTURE. [Pub. Doc. 



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 productiveness we call it an 

 injurious one. Now, this injurious influence may result even 

 when all the conditions in the new place are favorable to the 

 health and development of the plant ; it is an influence which 

 is wholly independent, so 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 to me from Paraguay in 1889 by Dr. Thomas Morong, 

 then travelling in that country. I grew it both in the house 

 and out of doors, and for two generations was unable to 

 make it set fruit, even though the flowers were hand-polli- 

 nated ; yet the plants were healthy and grew vigorously. 

 The third generation grown out of doors this year set fruit 

 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 

 degrees of crossing, as both Darwin and Wallace have pointed 

 out ; and it is pertinent to this discussion to endeavor to dis- 

 cover if there is any real connection between the two. 



It is well proved that crossing is good for the resulting 

 offspring, because the differences between the parents carry 

 over new combinations of characters or at least new powers 

 into the crosses. It is a process of revitalization, and, the 

 more different the stocks in desirable characters within the 

 limits of the variety, the greater is the revitalization ; and 

 frequently the good is of a more positive kind, resulting in 

 pronounced characters which may serve as the basis for neAV 

 varieties. In the cross, therefore, a new combination of 

 characters or a new power fit it to live better than its 

 parents in the conditions under which they lived. In the 

 case of change of stock we find just the reverse, which, how- 

 ever, amounts to the same thing, — that the same characters 

 or powers fit the plant to live better in conditions new 

 to it than plants which have long lived in those conditions. 

 In either case, the good comes from the fitting together of 



