1917] HARRIS & LAWRENCE—TISSUE FLUIDS 295 
The general average for the shrubs, half shrubs, and woody 
twiners of the rocky slopes is given by 
Achyranthes A=2.83, P=33.9 
Chiococca A=3.64, P=43.6 
Croton A=1.47, P=17.7 
Echites A=1.78, P=21.4 
Hypelate A=2.34, P=28.1 
Jatropha A=1.02, P=12.3 
Lantana A=1.60, P=19.2 
Lantana A=2.14, P=25.7 
Morinda A=1.76, P=21.2 
Philibertella A=1.51, P=18.2 
Solanum A=1.098, P=23.8 
Turnera A=3.39, P=40.7 
2.192 25.48 
General average 
Thus the concentrations determined for the smaller forms are 
practically as large as those for the more truly arborescent species. 
Combining all the ligneous perennials of the rocky slopes (that is, 
omitting from the whole series of determinations only Bromelia and 
Bryophyllum), we have for the general average of the species means 
or species constants: mean depression, 2.249°; mean concentra- 
tion, 27.000 atmospheres. 
Combining both arborescent and suffrutescent growth forms, 
excepting only the herbaceous Sesuvium Portulacastrum, Bromelia, 
Bryophyllum, and the cacti, the values for the 31 species means 
or constants of the two habitats recognized give the following 
averages: mean depression, 2.505°; mean concentration, 30.05 
atmospheres. By including the herbaceous perennial Sesuvium, 
the averages for 32 species means or determinations is changed 
to A=2.516, P=30. 18. 
COMPARISON OF CONSTANTS WITH THOSE FOR MESOPHYTIC 
REGIONS.—The first question to be answered in the analysis of these 
data is that concerning the relative values of osmotic concentration 
in the sap of desert and mesophytic plant organisms. Specifically, 
do the results of this study confirm those obtained by Frrrmnc” in 
“ Firtinc, H., Die Wasserversorgung und die osmotischen Druckverhiltnisse 
der Wiistenpflanzen. Zeitschr. Bot. 3:209-275- 1911. 
