Cuar. I.) ACTION OF THE PARTS. 15 
explains how Drosera can flourish in extremely poor peaty 
soil,—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 Von Raumer were given in the ‘ Botanische Zeitung.’t 
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  fiitterung:” ‘Bot. Zeitung,’ 1878. 
‘Nutrition of Drosera rotundifolia.’ Some account of the results was 
+ “Vegetationsversuche an Drosera given before the Phys.-med. Soc., 
rotundifolia mit und ohne Fleisch- Erlangen, July 9, 1877. 
