294 J- ARTHUR HARRIS AND JOHN V. LAWRENCE 
In view of the fact that the Long Island series here used is to be 
much increased, further discussion of the observed differences may 
be postponed until the more extensive data are worked up. 
A conspicuous difference in "the osmotic concentration of rain- 
forest and desert vegetation is of course to be expected after the 
demonstration of the differentiation of the sap properties of the plants 
of this and more mesophytic regions. Two fairly satisfactory sets 
of determinations for deserts are now available. The magnitude of 
the differences between the rain forest and these will give some indica- 
tion of the range of variation to be found in the mean osmotic con- 
centration of the fluids of the species of different vegetations. 
A comparison with the Arizona desert series of determinations 
made at the time of hibernal and vernal vegetative activity*' is made 
in the accompanying tables, IX-X. In these, averages^ are given for 
Table IX 
Comparison for Ligneous Perennials 
Jamaican Habitats 
Arizona Habitats 
Ruinate 
13-05 
22.01 
Rocky slopes 
Ridge forest 
11-54 
21.04 
Canyons 
Leeward ravines 
10.83 
17.30 
Arroyos 
9-73 
30.34 
Bajada slopes 
45.20 
Salt spots 
All habitats 
11.44 
24.97 
All habitats 
Table X 
Comparison for Herbaceous Plants 
Jamaican Habitats 
Arizona Habitats 
9-77 
15-94 
Rocky slopes 
Ridge forest 
8.63 
13-33 
Canyons 
7.59 
12.99 
Arroyos 
Windward habitats 
7-52 
20.53 
Bajada slopes 
23-57 
Salt spots 
All habitats ' 8.80 
15-15 
All habitats 
^ Studies on the summer vegetation have been made and will eventually be 
published. 
* The averages for the southwestern deserts are based on species determinations, 
not on means of determinations as in the Jamaica series. The difference in method 
is of no significance for present purposes. 
