<918 
Journal of Agricultural Research voi. xxvii, no. « 
COMPARISON OF CERTAIN OF THE DOMINANT OR TYPE INDICATOR SPECIES 
OF THE REGION CONSIDERED 
In the preceding section we discussed the average values of the con¬ 
stants for the various plant associations, pointing out the possible sources 
of error in such a method of comparison and referring to the desirability 
of a compariosn based on the individual species constants. 
Limitations of space preclude the making of such a detailed com¬ 
parison in this place, and it is reserved for publication at a later time. 
The chief indicator species of the region, and a detailed discussion of 
the physical conditions of the habitats in which they occur, may be 
found in the lists of species discussed by our predecessors (24), Their 
data, taken in combination with those presented in the tables of this 
paper, make possible for the reader a comparison of the individual 
species among themselves. 
COMPARISON OF TOOELE VALLEY WITH CERTAIN OTHER REGIONS WHICH 
HAVE BEEN INVESTIGATED 
Those who have read the various papers on the sap properties of the 
native* vegetation of other regions, cited in the introduction of this paper, 
will note that the osmotic concentrations reported in the Utah habitats 
are very high as compared with those generally found elsewhere. The 
only comparable values are those found by Cavara (j) in plants growing 
along the margins of salt-concentrating basins, by Fitting (5) in the 
extreme conditions of North African deserts, by Harris, Lawrence, and 
Gortner ( 12 ) in the most saline portions of the Arizona deserts, by 
Harris and Lawrence (1 5) in the more saline regions of the Jamaican 
coastal deserts, and by Harris and Lawrence (16) in the mangrove 
swamp. These results are in full agreement with the theory that the 
physicochemical properties of the leaf-tissue fluids furnishes an ex¬ 
cellent index of the physical and chemical conditions of the soil, and 
lends strength to the conclusion that only agricultural plants of ex¬ 
tremely short-growth periods, such as would enable them to mature 
fluring the period of more abundant soil moisture and lower salinity of 
the surface layers of soil, or which are capable of developing high osmotic 
concentration and electrical conductivity of their tissue fluids, may be 
expected to thrive under the more extreme conditions, unless these are 
modified by irrigation. 
A more detailed comparison of the constants of the plants of this 
region with those of other regions would be of interest from the eco¬ 
logical rather than from the agricultural side, and will not be attempted 
here. An investigation of other Utah and Arizona desert regions is in 
progress, and further discussion may await the completion of these" 
more extensive studies. 
BEARING OF THE RESULTS ON THE PROBLEM OF CROP PRODUCTION 
In discussing the results of their study of the botanical composition 
of the natural vegetation of Tooele Valley in relation to the physical 
factors of the soil, Kearney, Briggs, Shantz, McLane, and Piemeisel 
(24) point out that within limits, which are defined, “... all important 
variations in the character of the soil are clearly expressed in the ap¬ 
pearance and botanical composition of the plant covering. In other 
