VOLUME LXX 



NUMBER 4 



THE 



Botanical Gazette 



OCTOBER 1920 



PHYSIOLOGICAL ISOLATION BY LOW TEMPERATURE 



IN BRYOPHYLLUM 1 



C. M. Child and A. W. Bellamy 



(with SIX figures) 

 Introduction 



It has long been known that certain relations of dominance or 

 control and subordination exist between different parts of plants. 

 Among these relations the most general is the dominance of the 

 chief growing tip over other buds, branches, etc.; that is. over 

 other growing tips. That these relations are not specific for par- 

 ticular parts of the plant is shown by the fact that the growth and 

 development of a bud, for example, may be inhibited by the chief 

 growing tip of the plant, by a branch, or by a leaf. Moreover, 

 the fact has been established that the dominance of one part over 

 another is associated in some way with the metabolic activity of 

 the dominant part. When this "is inhibited, for example, by 

 inciosure of a growing tip in an atmosphere without oxygen, or in 

 plaster, the effect on other buds is essentially the same as if the 

 growing tip had been removed; that is, it is no longer dominant, 

 but may regain its dominance when the inhibiting conditions are 

 removed and it again becomes active. 



In various publications (Child 1-6) it has been pointed out 

 that this relation of dominance and subordination is not peculiar 

 to plants, but that similar relations exist in animals. In these 



1 From the Hull Zoological Laboratory, University of Chicago. 



249 



