Insectivorous plants / by Charles Darwin ; revised by Francis Darwin.

  • Charles Darwin
Date:
1908
Catalogue details

Licence: In copyright

Credit: Insectivorous plants / by Charles Darwin ; revised by Francis Darwin. Source: Wellcome Collection.

    33/404 page 15
    explains Low Drosera can flourish in extremely poor peaty 6oil,—in some cases where nothing but sphagnum moss grows, and mosses depend altogether on the atmosphere for their nourishment. Although the leaves at a hasty glance do not appear green, owing to the purple colour of the tentacles, yet the upper and lower surfaces of the blade, the pedicels of the central tentacles, and the petioles contain chlorophyll, so that, no doubt, the plant obtains and assimi- lates carbonic acid from the air. Nevertheless, considering the nature of the soil where it grows, the supply of nitrogen would be extremely limited, or quite deficient, unless the plant had the power of obtaining this important element from captured insects. We can thus understand how it is that the roots are so poorly developed. These usually consist of only two or three slightly divided branches, from half to one inch in length, furnished with absorbent hairs. It appears, therefore, that the roots serve only to imbibe water; though, no doubt, they would absorb nutritious matter if present in the soil; for as we shall hereafter see, they absorb a weak solution of carbonate of ammonia. A plant of Drosera, with the edges of its leaves curled inwards, so as to form a temporary stomach, with the glands of the closely inflected tentacles pouring forth their acid secretion, which dissolves animal matter, afterwards to be absorbed, may be said to feed like an animal. But, differently from an animal, it drinks by means of its roots; and it must drink largely, so as to retain many drops of viscid fluid round the glands, sometimes as many as 260, exposed during the whole day to a glaring sun. [Since the publication of the first edition, several experi- ments have been made to determine whether insectivorous plants are able to profit by an animal diet.] My experiments were published in ‘Linnean Society’s Journal,’* and almost simultaneouly the results of Kellermann and Yon Raumer were given in the ‘ Botanische Zeitung.’f My experiments were begun in June 1877, when the plants were collected and planted in six ordinary soup-plates. Each plate was divided by a low partition into two sets, and the * Vol. xvii., Francis Darwin on the futterung:” ‘Bot. Zeitung,’ 1878. ‘Nutrition of Drosera rotundifolia.’ Some account of the results was f “ Vegetationsversuche an Drosera given before the Phys.-med. See., rotundifolia mit und ohne Fleisch- Erlangen, July 9, 1877.
    digitised image 1
    digitised image 2
    digitised image 3