GRAVITATIONAL SENSITIVENESS OF THE ROOT-TIP. 267 
To apply this method to froots is not easy, since the tip is 
slimy and slippery, and in leguminous plants, which are especially 
Fig. 1. 
Sorghuim-seedling supported by its grain, 8: the vertical cotyledon, C, 
shows the result of geotropism. 
Figs. 2& 3e 
Sorghum-seedlings supported by the cotyledon C ; the hypocotyl bearing 
the grain S at its base shows geotropic curvature. 
adapted to geotropic experiments, the weight of the cotyledon 1s 
considerable *. 
* With Lathyrus articulatus, in which the seeds had been lightened by 
* the root in horizontal glass tubes, 
cutting off a part, I managed to fix the tip of 
but no definite’results were obtained. > 
" Ya 
