180 



TENDKIL-BEAKEKS. 



Chap. IV. 



these movements curvature from a touch is thus 

 caused.* In the first place it may be remarked that the 

 movement of nutation differs from that due to a touch, 

 in so far that in some cases the two powers are acquired 

 by the same tendril at different periods of growth ; 

 and the sensitive part of the tendril does not seem 

 capable of nutation. One of my chief reasons for doubt- 

 ing whether the curvature from a touch is the result 

 of growth, is the extraordinary rapidity of the move- 

 ment. I have seen the extremity of a tendril of 

 Passiflora gracilis, after being touched, distinctly bent 

 in 25 seconds, and often in 30 seconds ; and so it is 

 with the thicker tendril of Sicyos. It appears hardly 

 credible that their outer surfaces could have actually 

 grown in length, which implies a permanent modifica- 

 tion of structure, in so short a time. The growth, 

 moreover, on this view must be considerable, for if the 

 touch has been at all rough the extremity is coiled 

 in two or three minutes into a spire of several turns. 



When the extreme tip of the tendril of Echinocystis 

 caught hold of a smooth stick, it coiled itself in a 

 few hours (as described at p. 132) twice or thrice round 



* It occurred to me that the 

 movement of nutation and that 

 from a touch might be differently 

 affected by anaesthetics, in the 

 same manner as Paul Bert has 

 shown to be the case with the 

 Bleep-movements of Mimosa and 

 those from a touch. I tried the 

 common pea and Fassiflora gra~ 



cilis, but I succeeded only in ob- 

 serving that both movements were 

 unaffected by exposure for 1 hrs. 

 to a rather large dose of sulphu- 

 ric ether. ~In this respect they 

 present a wonderful contrast with 

 Drosera, owing no doubt to the 

 presence of absorbent glands in 

 the latter plant. 



