* Abhand. der Schles. Gesell. fr vaterl. Cultur, 1861, Heft i. An
excellent abstract of this paper is given in the Annals and Mag. of
Nat. Hist. 3rd series, 1863, vol. xi. pp. 188-197. [page 257]
within their cells is ordinarily in a state of expansion, but is
paralysed by irritation, or may be said to suffer temporary death; the
elasticity of the cell-walls then coming into play, and causing the
contraction of the stamens. Now the cells on the upper or concave side
of the bending part of the tentacles of Drosera do not appear to be in
a state of tension, nor to be highly elastic; for when a leaf is
suddenly killed, or dies slowly, it is not the upper but the lower
sides of the tentacles which contract from elasticity. We may,
therefore, conclude that their movements cannot be accounted for by the
inherent elasticity of certain cells, opposed as long as they are alive
and not irritated by the expanded state of their contents.
A somewhat different view has been advanced by other
physiologists namely that the protoplasm, when irritated, contracts
like the soft sarcode of the muscles of animals. In Drosera the fluid
within the cells of the tentacles at the bending place appears under
the microscope thin and homogeneous, and after aggregation consists of
small, soft masses of matter, undergoing incessant changes of form and
floating in almost colourless fluid. These masses are completely
redissolved when the tentacles re-expand. Now it seems scarcely
possible that such matter should have any direct mechanical power; but
if through some molecular change it were to occupy less space than it
did before, no doubt the cell-walls would close up and contract. But in
this case it might be expected that the walls would exhibit wrinkles,
and none could ever be seen. Moreover, the contents of all the cells
seem to be of exactly the same nature, both before and after
aggregation; and yet only a few of the basal cells contract, the rest
of the tentacle remaining straight.
A third view maintained by some physiologists, [page 258] though
rejected by most others, is that the whole cell, including the walls,
actively contracts. If the walls are composed solely of non-nitrogenous
cellulose, this view is highly improbable; but it can hardly be doubted
that they must be permeated by proteid matter, at least whilst they are
growing. Nor does there seem any inherent improbability in the
231