5o6 
J. ARTHUR HARRIS 
CONCLUSIONS 
The osmotic concentration of the tissue fluids of epiphytic Brome- 
liaceae, Orchidaceae, Piperaceae, and Gesneraceae is far lower than 
that of terrestrial vegetation. 
In the Jamaican montane rain forest where direct comparisons for 
individual habitats are possible, the epiphytes show from 37 to 60 per- 
cent of the concentration characteristic of herbaceous terrestrial 
vegetation, and from 28 to 45 percent of the concentration of ligneous 
terrestrial vegetation. 
In the Bromeliaceae, Orchidaceae, and Peperomia of the Piper- 
aceae, the osmotic concentration of the species of the Jamaican mon- 
tane rain forest is lower than that of the species of the hammocks of 
subtropical Florida. 
At some future time I hope to deal with the problem of the osmotic 
concentration of cryptogamic epiphytes and to obtain data on the 
inorganic and organic constituents of the fluids of epiphytes which 
will justify further discussion of the physiology of these ecologically 
remarkable forms. 
LITERATURE CITED 
Harris, J. A. 1917. Physical chemistry in the service of phytogeography. Science, 
n. ser. 46: 25-30. 
■ . 1918. On the osmotic concentration of the tissue fluids of desert Loran- 
thaceae. Mem, Torrey Club 17: 307-315. 
Harris, J. A., and Gortner, R. A. 19 14. Note on the calculation of the osmotic 
pressure of expressed vegetable saps from the depression of the freezing point, 
with a table for the values of P for A = .001° to A = 2.999°. Amer. Journ. 
Bot. i: 75-78. 
Harris, J. A., and Lawrence, J. V. 1916. On the osmotic pressure of the tissue 
fluids of Jamaican Loranthaceae parasitic on various hosts. Amer. Journ. 
Bot. 3: 438-455- Diag. 1-2. 
. 1917a. The osmotic concentration of the tissue fluids of Jamaican montane 
rain forest vegetation. Amer. Journ. Bot. 4: 268-298. 
. 1917&. Cryoscopic determinations on tissue fluids of plants of Jamaican 
coastal deserts. Bot. Gaz. 64: 285-305. 
. With the co-operation of R. A. Gortner. 19 16. The cryoscopic constants 
of expressed vegetable saps as related to local conditions in the Arizona 
deserts. Physiol. Res. 2: 1-49. 
