FULL-GROWN PLANT AND ITS PARTS 57 
in the soil. Some plants have also air roots (called 
aérial roots). Examine the air roots of the climbing 
ivy, which you must strip off very carefully, noticing 
how the groups of roots cling on. One side of the stem 
is literally covered with these roots. They grow away 
from the light toward the tree on which the ivy twines, 
and fasten it quite 
firmly to the tree. 
Air roots or 
braces are formed 
in the maize, the 
screw pine, etc. 
Air roots grow from 
the branches of the 
banyan tree of 
India, and striking 
into the ground 
brace the wide 
branching system 
of the stems. 

Fic. 87. Buttresses of silk-cotton tree, Nassau. 
Buttresses are formed partly of root and partly of 
stem at the base of the tree trunks where root and 
stem join. | 
The work of roots. The roots do several kinds of 
work for the plant. They serve to anchor plants to 
the soil, or in the case of certain climbing plants to 
fasten them to some object of support. They aid also 
