46 



BOTANICAL GAZETTE 



[JANUARY 



Stems were bent passively and fixed in this bent position by 

 ing their ends to a piece of wood (fig. 30). Such pieces were then 



suspended in 



xperiments 



were made a year ago, before the writer was aware of the influence 

 of the position of the leaf upon geotropic curvature and root forma- 

 tion, and in the expectation that passive bending of a stem would 

 lead to the production of roots on the convex side of the stem. 



be 



numerous 





were 



was concave. 



order to understand the details of this 

 figure it should be stated that the photograph 

 was taken 2 months after the beginning of the 

 experiment. The apical part of the stem had 

 been horizontal in the beginning, but had since 

 bent upward, the bending taking place behind 

 the second node. The side on which the roots were formed, there- 

 fore, had originally been the under side. The roots formed all 

 along the lower side of that part of the stem which at first was in 

 a horizontal position. Besides the small apical leaves, a large older 

 leaf had been left on the stem, and from this leaf the stem was 

 suspended. At the base of this large leaf and of the next 2 nodes 

 a strong root formation took place. This is what we should expect 

 on stems in which a leaf is left on the upper side. 



Fig. 30 also illustrates in another way the influence of gravi- 

 tation on root formation. The reader will notice that in the 



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