1903.] 



The Statolith-thcory of Geotropism. 



371 



for long periods, i.e., 40 — 82 minutes; these are, perhaps, not strictly 

 comparable with the other experiments, though in three out of the 

 four the shaken specimens were clearly more curved than the still ones. 

 If these are omitted, we have : — 



Shaken, curvature greater 15 



,, equals still 2 



Still, curvature greater 2 



The amount of curvature is not merely greater in a large majority of 

 cases, but also differs by a considerable percentage. 



Thus, taking the sum of the average curvatures in all thirty cases, 

 we get : — 



Still. Shaken. 



403°*7 600°*8 or 100 : 148-8 



Omitting the seven second readings (which give the sums — -still 62*1, 

 shaken 108*2), we get : — 



Still. Shaken. 

 341°-6 492°*6 or 100 : 144*2 



Finally, omitting the four cases of long exposure (which give — still 

 7 1*1, shaken 103*7), we get : — 



Still. Shaken. 

 270°*5 388°*9 or 100 : 143*8 



In another series of experiments the difference between the shaken 

 and still plants was much smaller. But we have reason to believe that 

 the failure depended on the small amplitude of vibration employed, 

 for when, in the last four experiments of the series, a more ample 

 vibration was adopted, there was once more a .well-marked increase in 

 geotropism in the shaken specimens. 



In none of our experiments have we seen such striking results as 

 those obtained by Haberlandt ; it must, however, be remembered that 

 his apparatus differs from, and is apparently more effective than, ours. 



Control Experiments (Heliotropism). 



The experiments were made in the same way as the last, except 

 that the seedlings were vertical instead of horizontal, so that the 

 starch would be made to vibrate on the basal instead of on the lateral 

 walls of the cells. The boxes had glass lids to admit the light, which 

 was given by incandescent gas. Care was taken that the distance 

 from the light of the still specimens was the same as that of the 

 shaken specimens. 



