498 
J. ARTHUR HARRIS 
The table brings out clearly two facts: 
1. That in all four families and in both Jamaica and Florida, the 
osmotic concentration of epiphytic forms is extremely low. 
2. That for the three groups represented in both regions the os- 
motic concentration oT the epiphytes (chiefly from the hammocks) of 
subtropical Florida is higher than that demonstrated in the Jamaican 
rain forest. The average difference is 1.57 atmospheres higher for 
the Bromeliaceae,^ 1.74 atmospheres higher for the Orchidaceae, and 
o. 24 atmospheres higher for the single species of Peperomia. 
The comparison may be made somewhat more analytically on 
the basis of the means for the genera. 
The constants in table 2 are averages of the species means of each 
of the genera. 
Table 2 
Genera of Jamaican and Floridian Epiphytes Arranged in the Order of the Average 
Osmotic Concentration of Their Species 
Jamaica 
Genus 
Pleurothallis 
Stelis 
Tillandsia 
Lepanthes 
Epidendrum 
Columnea 
Peperomia 
Guzmannia 
Octadesmia 
Florida 
Genus 
2.57 
2.65 
3.00 
3.28 
3.56 
4-33 
4.34 
449 
5.25 
2.90 
4-52 
4.58 
4- 97 
5- 09 
5.15 
5.55 
5-56 
5.83 
6.00 
6.05 
8.97 
Vanilla 
Spathiger 
Peperomia 
Auliza 
Tillandsia 
Anacheilium 
Guzmannia 
Catopsis 
Encyclia 
Polystachya 
Macradenia 
Dendropogon 
^ That the higher value for Floridian Bromeliaceae is not primarily due to the 
inclusion of Dendropogon usneoides ( = Tillandsia usneoides) is shown by the fact 
that if this species be omitted from the Florida series, the remaining 9 species average 
A = 0.433, P = 5.19, which are respectively 0.100 and 1. 1 9 greater than the Jamaican 
average. 
