208 BIOLOGICAL LECTURES. 



by lamplight, it was still incurved. Next morning it had 

 again straightened out. I have often, and admiringly, 

 repeated the experiment on primary and secondary tendrils, 

 have varied the time-interval between the shocks, and have 

 varied the number of shocks given, but they have never failed 

 to respond. Though in a few instances Sicyos tendrils did 

 not sensibly respond when given 20 to 30 stimuli, the majority 

 behaved like those of Ecliinocystis. 



Thereafter, a large and vigorous plant of Cncnmis maxima, 

 was experimented with. Series of 5 stimuli at intervals of one 

 second were given every \ minute, and in 6 minutes, i.e. after 

 60 stimuli, two had incurved very distinctly. After 14 minutes 

 one had curved through J- of a circle, the other through ]. 

 Three of different length and age were then chosen with 

 essentially similar outcome. The whole subject of tendril 

 movement, as viewed in the above light, opens up a wide field 

 for comparative and critical investigation. Why not merely 

 elongation of cells but growth in thickness of tissue should 

 then follow on the side away from that irritated, is not difficult 

 to understand, in view of De Vries' and Wortmann's studies of 

 protoplasmic movement. 1 



Equally must I take exception to Pfeffer's assertion that 

 Drosera tentacle does not inflect after contact stimulus. 

 Darwin stated that inflexion usually took place after three or 

 more touches, though this is denied by Pfeffer. I find that if 

 the leaves of D. rotnndifolia, D. intermedia or D. dichotoma 

 are healthy and secreting their viscous juice freely, two stimuli 

 with a time-interval between of at least 25 seconds, causes 

 powerful incurving, but only after a latent period of 55-70 

 seconds. Few things in the range of plant life have seemed 

 so impressive as watching Drosera tentacle after second stim- 

 ulus. To know that, as the seconds pass with apparently 

 no change in the tentacle, active though invisible molecular 

 movement is progressing which culminates after about 60 

 seconds in a steady, sweeping incurvation of the tentacle for 



1 McDougall's experiments (Hot. Gazette, Vol. XVIII, 1893) on the stimulation 

 and movements of tendrils, suggest broad lines of investigation that may yield 

 good results. 



