318 DIONZA MUSCIPULA. Cuap. XIIL 
dots now stood about 7,5 of an inch (127 mm.) 
nearer together than before. If we suppose the whole 
upper surface of the lobe, which was #27, of an inch 
in breadth, to have contracted in the same proportion, 
the total contraction will have amounted to about 
4, or +5 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. Burdon 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-expansion 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 on 
lobe were cut off close to their bases; and the three 
* ‘Proc. Royal Soc.’ vol. xxi. 
p. 495; and lecture at the Royal 
Institution, June 5, 1874, given in 
‘Nature,’ 1874, pp. 105 and 127. 
+ Nuttall, in his ‘Gen. Ame- 
rican Plants,’ p. 277 (note), says 
that, whilst collectirg this plant 
in its native home, “I had occa- 
sion to observe that a detached 
leaf would make repeated efforts 
towards disclosing itself to the 
influence of the sun; these at- 
tempts consisted in an undula- 
tory motion of the marginal] cilia, 
accompanied by a partial open- 
ing and succeeding collapse of 
the lamina, which at length ter- 
minated in a complete expansion 
and in the destruction of sensi- 
bility.” I am indebted to Prof. 
Oliver for this reference; but I de 
not understand what took place, 
