‘ 
1917] HARRIS & LAWRENCE—TISSUE FLUIDS 207 
It is idle to go further into these comparisons. It is clear that 
the ligneous plants of the Jamaican coastal desert, those of the 
rocky hills as well as of the more or less saline flats, are character- 
ized by concentration of tissue fluids about twice as great as those 
of the Cold Spring Harbor region. 
The extensive series of species studied by OHLWEILER™ suffer 
from the disadvantage (in relation to the present paper) of being 
assembled from their natural habitats and grown in a Botanical 
Garden. All, however, are forms capable of growth in the open at 
St. Louis. These show a range of from about 7 to about 24 atmos- 
Pheres. The average value of the 90 determinations is 14.96 
atmospheres. Thus, OHLWEILER’s St. Louis series agrees very 
closely with our own preliminary average for Long Island habitats. 
Here again the values are only about half as high as those deter- 
mined in the coastal deserts. 
COMPARISON OF CONSTANTS WITH THOSE FOR TUCSON REGION.— 
Turning to averages for a comparison of the concentration of the 
Sap of the Jamaican coastal and the Arizona desert floras, the 
results for ligneous perennials only are: Arizona series, 24.97 
atmospheres; Jamaican series, 30.05 atmospheres. Apparently 
concentration is somewhat greater in the Jamaican series. If the 
comparison between the two desert areas is to be drawn on a more 
analytical basis, it may be noted that the values determined for the 
trees of the coastal flats are of the same order of magnitude as those 
derived from the species of Atriplex examined in the Arizona salt 
Spots. For example: 
Atriplex canescens P=39.5 
Atriplex canescens P= 67.5 
Atriplex canescens angustifolia P=32.8 
Atriplex polycarpa P=52.0 
In the Jamaican coastal deserts the trees and shrubs from the 
rocky slopes show concentrations lower than those of the coastal 
flats. In the Arizona deserts the plants of the rocky slopes show 
far lower osmotic concentrations than do those of the salt spots. 
_ Comparing Arizona and Jamaican rocky slopes the results are: 
*4 OHLWEILER, W. W., The relation between the density of cell saps and the 
Senne pemet ot of ‘ict: Ann. Rept. Mo. Bot. Gard. 23:101-131. pl. 6. 1912. 
