34 



BOTANICAL GAZETTE 



[JANUARY 



or it is confined to the 

 front of the basal leaf 



(fig. 1 6). When 



Fig. 14 



place, more rapid and extensive than in fig. 15, but less rapid than 

 when the apical leaf is left, as in fig. 17. In the other halves of the 

 stem which were suspended with the cortex above (figs. 18, 19, 20), 

 practically no geotropic bending takes place, for the reason that 



Fig. 15 



the geotropic bending of the stem of Bryophyllum 



is due, as we shall see, to the active growth of the 

 cortex on the lower side, which is lacking in those 

 halves in which the cut surface forms the lower 



side, as in 



18-20. 



drawings 



made on the seventeenth day of the experiment. 



21 gives an indication of how regularly the 



results described in figs. 14-17 occur. 



It was of interest to study the reaction of split stems in which 



the leaf was above and the cortex below. For this purpose it was 



necessary to split the stem only to the apical or basal node in which 



the leaf was preserved (figs. 22, 23), but not in its entire length. 



