Plants That Feed on Insects. 25 
only can live. Although the leaves of the Droseras at a 
hasty glance do not appear green, owing to the purple color 
of the tentacles, yet the superior and inferior surfaces of the 
blade, the stalks of the central tentacles, and the petioles 
contain chlorophyll, rendering the best of evidence that the 
plants obtain and assimilate carbon dioxide from the air. 
But when the poverty of the soil where these plants grow is 
considered, it is at once apparent that their supply of nitrogen 
would be exceedingly small, or quite deficient, unless they 
had the power of obtaining it from some other source. From 
captured insects this important element is largely obtained, 
and thus we are prepared to understand how it is that their 
roots, which consist of only two or three slightly divided 
branches, from one-half to one inch in length, and furnished 
ROUND-LEAVED SUNDEW. 
Leaves Acting as Stomachs. 
