366 ' Mr F. Darwin and Mr R W. Phillips, [Nov. 23, 



Since bending (even twice) obviously did not seriously diminish 

 the lumen of the vessels we tried squeezing the branch with a 

 vice* — half the branch being cut away in order that the vice might 

 be used more conveniently. 



Exp. 39. Sept. 17, 1884. Bramble. 



Time 



5.52 



Eate 

 29-1 



Vice screwed up tight • 

 57 | 111 

 Vice slackened 

 59 | 35-9 

 Vice screwed up 



6.6 | 16-7 

 Vice slackened 



6.7 | 43-9 



Exp. 40. Sept. 20, 1884. Helianthus tuberosity. Conditions 

 of experiment similar in all respects to those of the last. 



Here again we get a considerable depression ; followed by a 

 temporary increase when the block is removed. 



It may be argued by an imbibitionist that the severe pressure 

 exercised by the vice may have injured the cell-walls by crushing 

 them and thus interfered with their transmitting qualities. 



The fact that the rate recovers when the vice is loosened shows 

 that the path of transmission, whatever it may be — cell-wall or 

 cavity — is not permanently injured, and it is easier to believe that 

 the lumen of a tube might recover its previous size, when the 

 pressure is removed, than that a crushed cell-wall should recover 

 its original properties. It may be added that the doctrine of im- 

 bibition seems to exclude the possibility of pressure affecting the 



* Vesque found that a willow branch could be made to wither by squeezing it in 

 a vice (Ann. Sc. Nat. 1884), Kohl has published experiments similar to ours. Bot. 

 Zeitung, 1885. 



