CONCENTRATION OF TISSUE FLUIDS OF EPIPHYTES 497 
A = 0.32, P = 3.9; Feb. 24, A = 0.36, P = 4.4; Mar. 2, A = 0.37, 
P = 4.5; Mar. 4, A = 0.38, P = 4-5; Mar. 13, A = 0.40, P = 4.8. 
ANALYSIS OF DATA 
In this paper I shall limit discussion of the data presented to a 
comparison of the constants of the epiphytes among themselves and 
with the values which have already been obtained for terrestrial forms 
in various habitats. Even these comparisons must be limited by the 
still unorganized condition of our data for several important habitats. 
Since, however, it will be many months before all of these data can be 
fully analyzed and ready for discussion, it has seemed proper to place 
the data which have been obtained for epiphytes during the past 
three years on record in a form which will enable other physiologists 
and phytogeographers to use them. 
Consider first of all the relative magnitudes of the osmotic con- 
centrations found in the epiphytic plants of the two regions considered. 
The results, grouped by families, are shown in table i. 
The constants in this table are the averages of species means, not of 
species determinations (except when only one determination is availa- 
ble for a species), for each family. While the species means which are 
based upon a large number of determinations are somewhat more 
trustworthy than those which are based upon only two or three 
readings, or upon only a single collection, the general mean for the 
habitat is certainly more representative when calculated in this way 
than if the habitat average had been computed directly from the 
individual constants, thus weighting the species with the numbers of 
collections of each which happened to be made. 
Table i 
Comparison of Osmotic Concentrations in Jamaican and Floridian Epiphytes 
Jamaica | Florida 
Difference 
Bromeliaceae 
Orchidaceae 
Piperaceae 
Gesneraceae 
A = 0.333, P = 4.00 
2 genera, 3 species 
A = 0.276, P = 3.32 
5 genera, 7 species 
A = 0.362, P = 4.34 
Peperomia only, 
5 species 
A = 0.358, P = 4.33 
Columnea hirsuta 
only 
A = 0.464, P - 5.57 
4 genera, 10 species 
A --= 0.421, P = 5.06 
7 genera, 7 species 
A = 0.380, P = 4.58 
Peperomia magnolia- 
folia only 
A = + O.131, 
P = + 1-57 
A = + 0.145, 
P = + 1.74 
A = + 0.018, 
P = + 0.24 
No representative. 
