

78 



BOTANICAL GAZETTE 



[JULY 





show little agreement. Some writers have found the greater 

 turgor on the concave, some on the convex, side; others have found 

 no difference in turgor in either flank of the stimulated shoot or in 

 the stimulated versus the unstimulated organ, with the balance 

 of the argument rather in favor of the last mentioned. Inspection 

 of the work of those writers who have tabulated their results, 

 however, shows that the time of stimulation (ranging in general 

 from several hours to several days) was too long to catch the 

 change in turgor, which change appears to take place in a relatively 

 short time, as was originally determined by DeVries in his macro- 

 scopic turgor experiments on geotropically stimulated grass nodes. 



Respiration 



Qualitative experiments were conducted upon the relative 

 respiration of stimulated and unstimulated roots, and upon the 

 upper and under flanks of geotropically stimulated shoots. These 

 experiments were made in the Tashiro (19) biometer apparatus, 

 which determines the relative rate of respiration by the precipitation 

 of barium carbonate on the surface of a drop of barium hydrate in 

 a closed chamber. 



The roots, without previous stimulation, were placed, one 

 horizontally and one vertically, in similar chambers designated 

 as left and right respectively. The shoots were stimulated for 

 periods varying from 10 minutes to 5 hours. They were split 

 longitudinally just before being placed in the apparatus. The 

 roots were suspended and the shoots were placed horizontally, 

 the upper with the cut surface down, and the lower with the cut 

 surface up, as during stimulation. Both were placed across Van 

 Tieghem cells in order to give equal opportunity for carbon dioxide 

 diffusion. Many seedlings were tested with uniform results. 



Table II shows that a geotropically stimulated root has a higher 

 rate of respiration than the unstimulated root, and that in the 

 stimulated shoot the under (convex) side shows a higher rate of 

 respiration than the upper (concave) side at all intervals of time 

 during stimulation and response that were investigated. It also 

 shows that the rate of respiration decreases as the time of stimu- 

 lation increases. 



