146 SOUTH AFRICAN BOTANY 
from the leguminous plants. This is another example 
of symbiosis. As a result of this remarkable arrange- 
ment, soil in which leguminous plants have been grown 
is richer in nitrates than it was before. It is also 
possible now to obtain tubercles from the roots of the 
leguminous plants and add them to a soil deficient in 
nitrates ; if a leguminous crop is then grown the soil 
will be enriched. 
121. Carnivorous or Insectivorous Plants obtain most 
of their nitrogenous food from the bodies of insects. 
They are found in swampy places, or in damp tropical 
forests, or they are epiphytes; hence they do not ob- 
tain salts from the soil as easily as other plants. Drosera, 
the sun-dew, is an insectivorous plant, of which several 
species are found in this country. The leaves: are 
small, round and covered with sticky, reddish-coloured 
hairs or glands. These glands secrete an acid fluid, and 
it is the glistening appearance of this that gives the 
plant its name. When an insect alights on the leaf, 
probably in search of honey, it is caught in the sticky 
secretion. The hairs then bend over, and finally the 
whole leaf curls up, enclosing the insect. The secreted 
fluid seems to have the power of digesting the solids in 
the insect’s body, which are thus absorbed by the plant. 
The leaf then uncurls, and the dried-up remains of 
the insect blow away. The tentacles will move when 
touched with any substance, but they will not curl over 
and pour out their digestive juice unless the substance 
is organic. A tiny scrap of raw meat, or white of 
egg will be digested just as the insect was. The so- 
called PITcHER-PLANTS have their leaves modified for 
