[page 362] Pinguicula or Nepenthes, for these plants are not at all
closely related to the Droceraceae. But the difficulty is not nearly so
great as it at first appears. Firstly, the juices of many plants
contain an acid, and, apparently, any acid serves for digestion.
Secondly, as Dr. Hooker has remarked in relation to the present subject
in his address at Belfast (1874), and as Sachs repeatedly insists,* the
embryos of some plants secrete a fluid which dissolves albuminous
substances out of the endosperm; although the endosperm is not actually
united with, only in contact with, the embryo. All plants, moreover,
have the power of dissolving albuminous or proteid substances, such as
protoplasm, chlorophyll, gluten, aleurone, and of carrying them from
one part to other parts of their tissues. This must be effected by a
solvent, probably consisting of a ferment together with an acid.** Now,
in the case of plants which are able to absorb already soluble matter
from captured insects, though not capable of true digestion, the
solvent just referred to, which must be occasionally present in the
glands, would be apt to exude from the glands together with the viscid
secretion, inasmuch as endosmose is accompanied by exosmose. If such
exudation did ever occur, the solvent would act on the animal matter
contained within the captured insects, and this would be an act of true
digestion. As it cannot be doubted that this process would be of high
service to plants
* Traite de Botanique 3rd edit. 1874, p. 844. See also for following
facts pp. 64, 76, 828, 831.
** Since this sentence was written, I have received a paper by
Gorup-Besanez ( Berichte der Deutschen Chem. Gesellschaft, Berlin,
1874, p. 1478), who, with the aid of Dr. H. Will, has actually made the
discovery that the seeds of the vetch contain a ferment, which, when
extracted by glycerine, dissolves albuminous substances, such as
fibrin, and converts them into true peptones. [page 363]
growing in very poor soil, it would tend to be perfected through
natural selection. Therefore, any ordinary plant having viscid glands,
which occasionally caught insects, might thus be converted under
favourable circumstances into a species capable of true digestion. It
ceases, therefore, to be any great mystery how several genera of
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