240 BOTANICAL GAZETTE [OCTOBER 
FooD OF EPIPHYTES.—Not only the water, which was running 
over the bark of the supporting tree, but also the indispensable 
mineral foods dissolved in it, are absorbed by the roots of the 
epiphytic fern. In the locality under discussion, as well as in the 
wet tropical forests where epiphytes are most abundant, there can 
be but minute traces of mineral dust from the forest covered soil 
Fic. 2.—Several clumps of polypody from near x in fig. 1, showing epiphytic 
lichens and liverworts, fruiting fronds of fern above, and young plants developed 
from prothallia below x at left; «3. 
blown by winds to the tree tops, to be washed down over the trunks 
by rains. It is evident, therefore, that the air plant is really de- 
pendent on the tree not only for support, in an advantageous posi- 
tion for light, but it must also rely on the tree to raise from the 
soil the food salts needed. In other words, the mineral-containing 
substances, resulting from the disintegration of bark, twigs, and 
leaves of the supporting tree (or perhaps a neighboring one), and 
