18 DROSEKA ROTUNDIFOLIA. CHAP. I. 



sphagnum inoss 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. 



