10 PEsSIN: EPIPHYLLOUS PLANTS OF JAMAICA 
Polypodium Phyllitidis and Mangifera indica. The leaves of 
Elaphoglossum latifolium were those chiefly used because of the 
abundance on them of epiphyllous liverworts in various stages of 
development. Sections of leaves of Mangifera indica were also 
studied to determine the relation of an epiphyllous lichen to the 
mango leaf. 
Sections of the leaves bearing epiphyllous hepatics showed 
characteristic thickened, club-like rhizoids arising in groups from 
the stem of the creeping liverwort. These rhizoids are sunken 
into the cuticle of the supporting leaf as if pressed in by some 
external force. The rhizoids broaden at their lower ends and 
flatten out as is shown in TEXT-FIG. I. This is true even of the 
rhizoids of one epiphyllous liverwort when growing upon another, 
for one sometimes finds two or more tiers of epiphylls growing 
upon a fern or a dicotyledon. . The rhizoids of the upper hepatic 
are in such cases decidedly flattened against the delicate leaves 
of the lower liverworts. This too is shown in the figure. The 
important point to be noted is that the rhizoids of the epiphyllous 
form were not observed to penetrate the tissues of the supporting 
leaf. Nor was there evident any abnormality in the internal 
structure of the supporting leaf, such as might conceivably be 
produced by the shade or by the weight of the epiphylls on the 
leaf or, possibly, by some substance such as an organic acid 
excreted by the rhizoids on the liverwort. 
The leaves of Mangifera indica bore numbers of orange-red 
disk-like plants of a species of Phycopeltis. Among these orange- 
red specks there were also minute grey patch-like lichens resem- 
bling those described by Cunningham (3) and Ward (9). The 
relation between these lichens and the mango leaf on which they 
grew has not been definitely determined. The sections of the 
mango leaf thus far studied showed no modifications of its tissues 
and no penetration by the lichens. 
DISCUSSION 
The problem of the evolutionary origin and individual develop- 
ment of the epiphyllous plants is a complex one which still requires 
much careful investigation. Schimper (4) observed that epiphytic 
seed plants commonly originate on their support through seeds. 
