CONCENTRATION OF TISSUE FLUIDS OF EPIPHYTES 
If the comparison be made with the ligneous terrestrial vegetation, 
the differences are —6.07 for the Leeward and —545 for the Windward 
habitats. 
In relative terms, the osmotic concentrations of the sap of the 
epiphytic Orchidaceae is only 37.3 to 46.5 percent as high as that of 
the terrestrial herbs of the same habitat, the constants for the Bromeli- 
aceae range from 42.3 to 49.6 percent of the comparable values for 
terrestrial herbs, while the determinations based on Peperomia range 
from 52.9 to 60.1 percent of those for the non-epiphytic herbs of the 
same habitats. Columnea shows a concentration of 56.9 percent of 
that of herbaceous plants in the Windward habitats and 62.7 percent 
of that of herbaceous plants in the Leeward habitats. If compared 
with ligneous terrestrial vegetation it shows a concentration of 44.0 
percent in the Windward and of 44.0 percent in the Leeward habits. 
Summarizing the results of this comparison : the osmotic concentra- 
tion of the fluids of the epiphytic Orchidaceae, Bromeliaceae, Piper- 
aceae, and Gesneraceae of the montane rain forest of Jamaica is roughly 
speaking only 37.3 to 62.7 percent as high as that of the terrestrial 
plants of the same region. 
The averages for herbaceous forms include, as already explained, a 
few determinations based on species which may occur on the ground or 
as epiphytes. They also include those based on a few ferns and fern 
allies. The removal of these constants might change slightly the actual 
values of the difference in the table. Since the forms which have been 
classified as terrestrial but may occur as epiphytes are characterized by 
lower osmotic concentration than the vegetation as a whole, the re- 
moval of these species from the list of herbaceous plants would make 
the differences demonstrated between terrestrial and epiphytic vege- 
tation even larger. The exclusion of the few determinations for 
terrestrial ferns and fern allies could be justified only on the assump- 
tion that they are sensibly differentiated in their sap properties from 
flowering plants. There is, at present, no basis for such an assumption. 
The low concentration of the sap of epiphytic Phanerogams may 
perhaps be most clearly brought out by comparing it with that of the 
ligneous species upon which they may occur. Table 5 gives the 
differences and relative concentrations for the Jamaican materials. 
Epiphytic Orchidaceae show from 28 to 36 percent, the epiphytic 
Bromeliaceae from 32 to 38 percent, the epiphytic Piperaceae from 
39 to 45 percent, and the epiphytic Gesneraceae about 44 percent 
