2o8 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 majoritv 

 behaved like those of Echinocystis. 



Thereafter, a large and vigorous plant of Ciicin)iis niaxinux, 

 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 incur\-ed very distinctly. After 14 minutes 

 one had curved through |^ of a circle, the other throuo;h '?. 

 Three of different length and age were then chosen v\'ith 

 essentially similar outcome. The whole subject of tendril 

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

 for comparative and critical in\'estigation. Why not mcreh- 

 elonofation 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.' 



Equally must I take exception to Pfeffer's assertion that 

 Droscra tentacle does not inflect after contact stimulus. 

 Darwin stated that inflexion usually took place after three or 

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

 the leaves of D. rotiiiidifolia, D. intcnncdia oi" D. dichotoma 

 are health)' and secreting their \iscous juice freely, two stimuli 

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

 powerful incurx'ing, but onl}' after a latent period of 55-70 

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

 so impressive as watching Droscra tentacle after second stim- 

 ulus. To know that, as tlie seconds pass with apparentl}- 

 no chantre in the tentacle, active though invisible molecular 

 movement is progressing which culminates after about 60 

 seconds in a steady, sweeping incur\'ation of the tentacle for 



' McDougall's experiniL-iUs (A'c/. Cuizctti, \'ol. .\\'III, iSc)3) on the- stiimilation 

 and movements of tLiidrils, sinisjcsl l)ioad lint-s of invcstiijation tliat may yield 

 good results. 



