decoction; and it is clear that the immersion of cabbage-leaves for an
hour in water at the boiling temperature is much more efficient in
extracting matter which excites Drosera than immersion during many
hours in warm water. Perhaps the contents of the cells are protected
(as Schiff remarks with respect to legumin) by the walls being formed
of cellulose, and that until these are ruptured by boiling-water, but
little of the contained albuminous matter is dissolved. We know from
the strong odour of cooked cabbage-leaves that boiling water produces
some chemical change in them, and that they are thus rendered far more
digestible and nutritious to man. It is therefore an interesting
* The leaves of young plants, before the heart is formed, such as were
used by me, contain 2.1 per cent. of albuminous matter, and the outer
leaves of mature plants 1.6 per cent. Watts Dictionary of Chemistry,
vol. i. p. 653. [page 84]
fact that water at this temperature extracts matter from them which
excites Drosera to an extraordinary degree.
Grasses contain far less nitrogenous matter than do peas or cabbages.
The leaves and stalks of three common kinds were chopped and boiled for
some time in distilled water. Drops of this decoction (after having
stood for 24 hrs.) were placed on six leaves, and acted in a rather
peculiar manner, of which other instances will be given in the seventh
chapter on the salts of ammonia. After 2 hrs. 30 m. four of the leaves
had their blades greatly inflected, but not their exterior tentacles;
and so it was with all six leaves after 24 hrs. Two days afterwards the
blades, as well as the few submarginal tentacles which had been
inflected, all re-expanded; and much of the fluid on their discs was by
this time absorbed. It appears that the decoction strongly excites the
glands on the disc, causing the blade to be quickly and greatly
inflected; but that the stimulus, differently from what occurs in
ordinary cases, does not spread, or only in a feeble degree, to the
exterior tentacles.
I may here add that one part of the extract of belladonna (procured
from a druggist) was dissolved in 437 of water, and drops were placed
on six leaves. Next day all six were somewhat inflected, and after 48
hrs. were completely re-expanded. It was not the included atropine
74