318 DIONiEA MUSCIPULA. Chap. XHI. 



dots now stood about tijVo ^^ ^^ i^oli ('127 mm.) 

 nearer together than before. If we suppose the whole 

 upper surface of the lobe, which was -^^^ of an inch 

 in breadth, to have contracted in the same proportion, 

 the total contraction will have amounted to about 

 -^-^^ or ^V of an inch (-635 mm.) ; but whether this 

 is sufficient to account for the slight inward curvature 

 of the whole lobe, I am unable to say. 



Finally, with respect to the movement of the leaves, 

 the wonderful discovery made by Dr. Burden Sander- 

 son* is now universally known ; namely that there 

 exists a normal electrical current in the blade and 

 footstalk ; and that when the leaves are irritated, the 

 current is disturbed in the same manner as takes place 

 during the contraction of the muscle of an animal. 



The Re-ex]pansion of the Leaves. — This is effected at an 

 insensibly slow rate, whether or not any object is 

 enclosed.t One lobe can re-expand by itself, as oc- 

 curred with the torpid leaf of which one lobe alone had 

 closed. We have also seen in the experiments with 

 cheese and albumen that the two ends of the same lobe 

 can re-expand to a certain extent independently of 

 each other. But in all ordinary cases both lobes open 

 at the same time. The re-expansion is not determined 

 by the sensitive filaments ; all three filaments on one 

 lobe were cut off close to their bases ; and the three 



* 'Proc. Royal Soc' vol. xxi. influence of the sim; these at- 



p. 405 ; and lecture at the Royal tempts consisted in an undula- 



Institution, June 5, 1874, given in tory motion of the marginal cilia3, 



'Nature,' 1874, pp. 105 and 127. accompanied by a partial open- 



t Nuttall, in his 'Gen. Ame- ing and succeeding collapse of 



rican Plants,' p. 277 (note), says the lamina, wliich at length ter- 



that, whilst collecting this plant minated in a complete expansion 



in its native home, " I had occa- and in the destruction of sensi- 



Bion to observe that a detaclicd bility." I am indebted to Prof, 



leaf would make repeated efibrta Oliver for this reference ; but I do 



towards disclosing itself to the not understand what took place. 



