174 
EPIPHYTES 
(except carbon) becomes more difficult. Most of them are 
excellently suited in structure and physiology to their mode 
of life, and yet possess few or in some cases no true adapta- 
tions to it. The group is made up of a number of genera 
which happen to possess in common a number of charac- 
ters — adaptations to various ends — which enable their pos- 
sessors to become epiphytic. The ferns, Bromeliaceae, 
Orchidaceae and Araceae are largely represented in the 
group ; important genera of epiphytes, not belonging to 
these families, are Piper, Clusia, Phyllocactus, Rhipsalis, 
Columnea, Dischidia, Aeschynanthus, Hydnophytum, Myr- 
mecodia, &c. 
In the first place, no plant can become epiphytic unless 
it has an excellent seed-dispersal mechanism. Wind and 
birds are the only agents capable of regularly carrying the 
seeds to sufficient heights. All epiphytes possess either 
wind or bird mechanisms. Interesting observations may 
be made on this part of the subject by studying the flora 
of pollard trees in Europe ; many species occur in the bowls 
of humus at the tops of willows, &c., almost all wind- and 
animal-dispersed; about 15 °/o of the species (3% of the 
individuals) have mechanisms incapable of transporting 
their seeds to the requisite height, and of these many are 
carried up, more or less accidentally, by birds in nest- 
making. 
In the second place, a species to become a successful 
epiphyte must be able to fasten itself to its support, and 
at once after germination. Just as in Europe plants with 
good dispersal-methods may become epiphytes in willows, 
where there is plenty of food and no difficulty in anchorage, 
so in the tropics many become accidental epiphytes in the 
leaf-sheaths of Palms, or in the pitchers of Bromeliaceae, 
and so on. True epiphytes however are able to cling to 
almost any support at any angle, usually by means of clasp- 
ing roots of the kind found in root-climbers. Such roots 
are always adventitious, developed from the stem ; thus we 
can perhaps understand why Monocotyledons form so large 
a proportion of the epiphytic flora. Tap-rooting plants, 
as so many of the Dicotyledons are, would not be able 
to cling to their supports in time to prevent falling off. 
One group of epiphytes, the Araceae seems to have 
