in 1 7] 



WEB— BR YOPHYLL UM 



47 



stem 



node. This occurs only after a long time and 

 side of a stem. 



from 



The experiment demonstrates, therefore, that roots will form 

 on the concave side of a passively bent stem of Bryophyllutn caly- 

 cinum if this side is the under side of such a stem. 



viii. Theoretical remarks and summary 



theoretical remarks may be brief. We believe 

 ts show first that in Bryophyllum calycinun, 



a 



Fig. 29 



stances which induce root formation 

 have a tendency to collect on the lower 

 side of a horizontally placed stem, 

 although roots may appear also in 

 nodes on the upper side (especially at 

 the basal nodes), under special condi- 

 tions which will be discussed in another 



paper 



this 



a horizontally suspended stem of Bryophyllum will become concave 

 on the upper side, and that this curvature, which will give such a 

 piece a U-shape, is due to a longitudinal growth of the cortex on 

 the under side of the horizontally suspended stem. 



2. We have seen that a leafless stem bends much more slowly 

 than a stem in which one or more leaves are preserved; and we find 



