for instance, by bringing 
about chemical changes 
that might aid in the 
work of nutrition. 
87. Epiphytes, or air 
plants. —In the proper 
meaning of the word 
these are not parasitic, 
but use their host merely 
as a mechanical support 
to bring them into better 
light relations. The 
name, however, is loosely 
applied to all plants that 
find a lodgment on the 
trunks and branches of 
trees, whether parasites 
or true epiphytes that 
draw’ no nourishment 
from the host. Not in- 
frequently the latter is 
killed by them through 
suffocation, overweight- 
ing, or the constriction 
of the stems by close 
clinging twiners. 
88. Aérial roots are 
such as have no connec- 
tion at all with the soil or 
with any host plant, ex- 
cept as they may lodge 
upon the trunks and 
branches of trees for a 
support. In other than 
purely epiphytic plants, 
which get all their nour- 
THE ROOT 77 
Fig. 90.—A single strand of Tillandsia 
usneotdes, a rootless epiphyte belonging to the 
pineapple family ; better known as the ‘‘ Span- 
ish moss’’ that drapes the boughs of trees so 
conspicuously in the warm parts of America. 
Two-thirds natural size. (Photographed by C. 
F..0’Keefe.) : 
