— 127 — 



curvature may be possible and this I find to be the case to a con- 

 siderable extent. 



The experiments consist in fixing Sorghums horizontally, either 

 in tubes or in gypsum, until they curve upwards through some 

 40— 50°, they are then reversed, i. e., the cotyiedon, by which they 

 are supported, is rotated through 180", and they are left in the new 

 Position until they have again curved markedly upwards. They are 

 then carefully sketched so as to show the degree to which the 

 first curvature is still visible. The experiments were made in damp 

 air in the dark at a temperature of 24—25". 1 am indebted to Miss 

 Pertz for making the tracings shown in the accompanying figures. 



Experiment 1. After 2 hours the seedling had curved upwards 

 through 45", it was then reversed and after 5V2 hrs. it was at 



Fig. 1. Fig. 2. Fig. 3. 



+ 40" having curved through 85". The first curve was still faintly 

 visible (about 5^^). 



Experiment 2. In 6 hours curved to + 40", then reversed and 

 in I7V3 hrs. curved through 80" (to + 40"). The first curve still 

 visible (= about 12°). 



Experiment 3. In 3 hours curved to + 40"; reversed and in 

 24 hours curved to + 45" (i. e,, through 85"). The first curve distinctly 

 visible = about 15". 



Experiment 4. Curved through 75" when reversed, and showed 

 a mere trace of the original curve. 



Experiment 5, fig. 1. May 4, 1Q07. In 5V2 hours curved 

 through 102", reversed and in 20 hours curved trough 15ö". The 

 first curve is visible (= about 15"). 



Experiment 6, fig. 2. May 4, 1Q07. In 5^1^ hours curved 

 through 30", reversed and in 20 hours curved through 165". The 

 first curve is visible (= about 12"). 



