CHAPTER XXVIII 
PECULIARITIES OF PLANT LIFE 
311. Unusual Plants. — In order to live, all plants must 
have conditions favorable to their vital processes, and 
many of them develop special modifications which aid them 
in the struggle for existence. Some of the modifications 
already studied in this book are the arrangement of leaves 
or the length of petioles to secure air and light; the presence 
of color, odor, and nectar, devices to attract insects and 
thus secure the pollination of flowers ; and the use of wings, 
pappus, and hooks to secure the distribution of seeds. Many 
of the carnivorous (Figures 337, 338, 339) and parasitic plants 
are remarkable for the 
modifications which make 
it possible for them to ob¬ 
tain nitrogen, an element 
lacking in the food supply 
of their particular en¬ 
vironment. 
The Pitcher Plant. —■ 
The leaves of this plant 
form a sort of vase which 
retains water in the bot¬ 
tom. When insects crawl into the leaf, their escape is pre¬ 
vented by hairs which grow around the opening on the inside 
and point downward, and the unfortunate victim, exhausted 
by his struggles to get out, falls into the water and is drowned. 
When the bodies decay, the plants secure the nitrogen which 
they are unable to get through their roots. 
366 
Figure 337. — Leaves of Pitcher Plant. 
