224 Groom —On Dischidia rafflesianct (Wall.). 
and laterally compressed : the aperture or mouth is small 
and its lips are deeply incurved (see Fig. i). The mouth is 
directed upwards or downwards, towards or away from the 
support. The plant climbs by means of adventitious roots 
which spread over the bark of the host-tree, and even dip 
beneath any loose portions of the bark. The stem, or the 
stalk of the pitcher, gives off a second class of roots which 
enter and ramify within the cavity of the pitcher. 
Concerning the fact that D. raffle siana is specially found on 
decaying trees, a few explanatory remarks may be ventured 
upon. Schimper 1 shows that the distribution of South 
American epiphytes is, within their own region, largely 
determined by : (i) their relative demands for light and 
moisture, some epiphytes requiring more light and a less 
constant supply of moisture than others ; (2) the denseness or 
lightness of the foliage of the host-plant, including the 
deciduous or evergreen character of the latter ; (3) the nature 
of the bark or surface of the host-plant, epiphytes for the 
most part avoiding trees with a very smooth surface or with 
a peeling bark ; (4) the nature of the host, epiphytes showing 
a decided preference for certain trees in a manner at present 
not wholly explicable. In the case of a decaying tree the 
foliage will be less dense, consequently any epiphyte upon it 
will receive more light and a larger direct supply of rain- 
water, than if the tree were healthy. The air and the soil in 
the neighbourhood of this lightly-foliaged tree will be, on the 
average, drier, and the humus on its surface will be more 
rapidly decomposed. Thus, in a moist climate, an epiphyte 
on a decaying tree will have at its disposal a larger amount 
of available food than if it grew on a healthy tree of the same 
sort. This would seem to explain the fact mentioned by 
Schimper 2 , that in the moist and equable climate of Jamaica 
Aspidium nodosum can live on decaying trees (not on healthy 
ones) : whereas in Trinidad, which has a more marked dry 
1 Schimper, Die epiphytische Vegetation Amerikas (Botan. Mittheil. aus den 
Tropen, Heft 2, Jena). 
2 Schimper, loc. cit. 
