M. Vogel has shown* that the flowers of various plants do not wither so
soon when their stems are placed in a solution of camphor as when in
water; and that if already slightly withered, they recover more
quickly. The germination of certain seeds is also accelerated by the
solution. So that camphor acts as a stimulant, and it is the only known
stimulant for plants. I
* Gardener s Chronicle, 1874, p. 671. Nearly similar observations
were made in 1798 by B. S. Barton. [page 210]
wished, therefore, to ascertain whether camphor would render the leaves
of Drosera more sensitive to mechanical irritation than they naturally
are. Six leaves were left in distilled water for 5 m. or 6 m., and then
gently brushed twice or thrice, whilst still under water, with a soft
camel-hair brush; but no movement ensued. Nine leaves, which had been
immersed in the above solution of camphor for the times stated in the
following table, were next brushed only once with the same brush and in
the same manner as before; the results are given in the table. My first
trials were made by brushing the leaves whilst still immersed in the
solution; but it occurred to me that the viscid secretion round the
glands would thus be removed, and the camphor might act more
effectually on them. In all the following trials, therefore, each leaf
was taken out of the solution, waved for about 15 s. in water, then
placed in fresh water and brushed, so that the brushing would not allow
the freer access of the camphor; but this treatment made no difference
in the results.
Column 1 : Number of Leaves. Column 2 : Length of Immersion in the
Solution of Camphor. Column 3 : Length of Time between the Act of
Brushing and the Inflection of the Tentacles. Column 4 : Length of Time
between the Immersion of the Leaves in the Solution and the First Sign
of the Inflection of the Tentacles.
1 : 5 m. : 3 m. considerable inflection; 4 m. all the tentacles except
3 or 4 inflected. : 8 m.
2 : 5 m. : 6 m. first sign of inflection. : 11 m.
191