1920] CHILD 6* BELLAMY— BRYOPIIYLLUM 263 



number of buds developing and degree of development, has occurred 

 in the experimental leaf and the leaf opposite. 



In these experiments generally the buds which do not develop 

 distinct shoots as well as roots within a week, either do not develop 

 shoots at all, or give rise to shoots which grow very slowly and 

 often soon cease to grow. Such buds are evidently inhibited to a 

 greater or less degree. Apparently they represent somewhat less 

 active or weaker buds, which react less rapidly than others to the 

 isolating conditions, and so do not advance far enough before the 

 return of the experimental leaf to normal conditions to maintain 

 their growth afterward. 



It appears true also that in general buds give rise only to 



roots when the degree of physiological isolation is relatively slight. 



while with more complete isolation shoots as well as roots appear. 



The length of the isolation period is probably also a factor, since 



the outgrowth of roots begins somewhat earlier than that of the 



shoots, or at least occurs more rapidly during the early stages. A 



brief period of isolation gives time for roots to appear, but a 



longer period is apparently necessary for the shoot to become well 



started. 



Discussion 



It is evident from these experiments that a mere cooling of a 



tphyll 



rowing 



tip and other parts upon the buds of that leaf, and also the inhibit- 

 ing action of the leaf upon the buds of the opposite leaf and other 

 leaves in the same region of the plant. That this cooling does not 

 block the flow of fluids and substances in solution through the 

 vascular bundles is indicated by the experimental fact noted that 

 leaves show no wilting in an atmosphere in which leaves severed 

 from the plant wilt. In the case of the bean seedling, to be dis- 

 cussed in a later paper, this is still more clearly evident, for there 

 the zone of low temperature is placed about the main stem, and 

 all substances passing from below to those parts of the plant above 

 the cooled zone must of course pass through it. In such cases 

 there is no wilting of the parts above the zone, and growth is 

 either not at all inhibited, or, when the region cooled is young 



