164 
PLANT STUDIES 
This association of insects and flowers is sometimes so 
intimate that they have come to depend absolutely upon 
one another. Especially among the orchids is it true that 
special flowers and insects are adapted so exactly to one 
another, that if one dis- 
appears the other be- 
comes extinct also. 
122. " Carnivorous " 
plants. This name has 
been given to plants 
which have developed 
the curious habit of 
capturing insects and 
using them for food, 
and perhaps they had 
better be called " insec- 
tivorous plants." They 
are green plants and, 
therefore, can manu- 
facture carbohydrates. 
But they live in soil 
poor in nitrogen com- 
pounds, and hence pro- 
teid formation is inter- 
fered with. The bodies 
of captured insects sup- 
plement the proteid 
supply, and the plants 
have come to depend 
upon them. Many, if 
not all, of these car- 
nivorous plants secrete 
a digestive substance 
which acts upon the 
bodies of the captured insects very much as the diges- 
tive substances of the alimentary canal act upon proteids 
FIG. 154. The Californian pitcher plant (Dar- 
lingtoniti), showing twisted and winged pitch- 
er, the overarching hood with translucent 
spots, and the fish-tail appendage to the hood 
which is attractive to flying insects. After 
KEENER. 
