534 
On Tropical Epiphytes. 
[September, 
secondary roots. The seeds are adapted for distribution by 
the wind or by animals ; some of them are arranged for what 
may be called flight ; others are exceptionally light ; and 
others, again, are enclosed in juicy fruits. In many epi- 
phytes we meet, besides, with a non-sexual repiodudtion by 
means of stolons, or shoots, which subsequently become^ in- 
dependent, and which in some cases, as in Tillandsia usneoides, 
entirely supersede sexual reproduction. 
The Epiphytes, as regards their manner of life, may be 
divided into four groups. The first class comprises those 
plants which for their whole lifetime obtain their nutriment 
solely from the surface of the bark to which they have be- 
come attached. The second and third classes are thus 
dependent on their support in their youth only, and the 
fourth never. These plants procure a more plentiful supply 
of nourishment, either by aerial roots which they send down 
into the soil (second group) ; or by roots which form an ex- 
tended tissue, of a sponge-like character, in which moisture 
and humus accumulate in abundance (third group) ; 01, 
lastly, the leaves and stems perform the fundhon, generally 
peculiar to roots, i.e., the intus-susception of food (fourth 
§1 In P the first group, on the lowest stage of adaptation to an 
epiphytic life, we find forms which, like ground-plants, take 
up their nourishment by means of capillary roots. Many 
such species live, therefore, exclusively on the bark of very 
old trees rich in nutritious matter and full of chinks, borne 
occur only in very moist forests. To this group there belong 
certain Polypodiums (some of the European representatives 
of which genus are well known as growing on the stems of 
deravine trees), Peperomia, Columned , Rhipsahs, &c. 
Bette? adapted aYe the orchids and aroids. Their roots 
are fitted with a peculiar coating, capable of absorbing 
water and technically known as the velamen. This 
covering is partially lost only in an advanced age. Here, as 
in the former group, the roots penetiate into the fissuiesand 
hollows of the bark. They contain a little chlorophyll, but 
their power of assimilating carbon is feeble, as they are 
enclosed in the velamen and are negatively hehotropic, 
turning away fiom the light. 
In the leafless short-stemmed Aeranthes funahs the roots, 
which form the main bulk of the plant, perform all the 
functions of vegetation. These roots are green, and hang 
for the most part freely in the air. In accordance with the 
slight development of leaf and stem, and the reduced tians- 
piration, the vascular bundle of the roots is thin and contains 
