18 DROSERA ROTUNDIFOLIA. Cuar. I. 
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 assimilates 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 under- 
stand 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 in- 
wards, 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. 
