COHN, ON THE CONTRACTILE FILAMENTS OF THE CYNAREX. 187 
In many Cynarez, when the irritability is not manifested, 
this will be found to arise from the circumstance that the 
flowers have been examined at too late a period. As a rule, 
it may be said to be too late when the stigma is visible above 
the anther-tube. 
As is well known, the cause of these phenomena resides 
wholly and solely in the filaments, which each time they are 
touched instantly contract, and after a while extend them- 
selves to their original length. The expulsion of the pollen 
from the anther-tube depends upon the circumstance that the 
tube, as the filaments shorten, is drawn downwards on the 
pistil about 1—2 mm., and is afterwards pushed upwards 
again. The contractility of the filaments is shown in the 
most interesting manner in preparations in which nothing 
but the anther-tube is left, and in which the five filaments 
have been cut away from the corolla, and thus rendered free 
to move independently. Under these circumstances they 
exhibit the liveliest irritability whenever they are touched ; 
retracting themselves, bending and twisting out, and again 
becoming extended, and then bending over on the opposite 
side, twining themselves together, &c., so that it is hardly 
possible to escape the impression that we are witnessing the 
movements of a Hydra, and not those of any part of a plant. 
Professor Cohn has, on a former occasion,* pointed out 
the laws by which these motions are regulated, and the con- 
clusions he then arrived at have since been confirmed by the 
further observations of Kabscht} and of Unger.{ 
He has shown that the contractile filaments were ener- 
getically affected by the electric current ; contracting instantly 
under a feeble current, but again extending themselves after 
a time, and then again manifesting irritability. 
A powerful current Xil/s the filaments instantly; the conse- 
quence of which is that the contractile filaments do not again 
extend themselves, but, on the contrary, continue to contract 
more and more, until at the end of about an hour they are 
not more than half their original length. 
When killed by other means, as, for instance, by immersion 
in alcohol, glycerine, or water, a similar shortening of the 
filaments to less than half their original length is observed ; 
it is clear, therefore, that this contraction cannot be due 
simply to a shrinking, from desiccation. It may also be 
* Ina paper in the ‘Abhandl. d. Schlesisehen Gesellschaft. f. Vaterl. 
Cultur,’ 1861. (An abstract of this valuable paper, by Dr. Arlidge, will be 
found in the ‘ Annals of Nat. History’ for March, 1863.) 
+ ‘Botanisch. Zeitung,’ 1861. 
t Ibid., 1862. 
