920 
Journal of Agricultural Research voi. xxvn, No. i* 
As far as we yet know, few agricultural plants are capable of tolerating 
salts in such quantities as are present in the soil in certain of these habi¬ 
tats, or of developing the osmotic concentrations which enable them 
to withdraw water from soil of such texture, salinity, and dryness. 
A detailed discussion of the bearing of the results of the present study 
of natural vegetation on the problem of crop production in the arid and 
saline regions is limited by the inadequacy of our published knowledge 
of the physicochemical properties of the tissue fluids of agricultural 
plants. The pertinent facts are being rapidly supplied by detailed 
investigations which have been under way for the past three years on the 
important agricultural plants of the western United States, such as the 
small grains, the grain sorghums, com, and cotton. 
Studies on the small grains at the Nephi substation of the Utah Agricul¬ 
tural Experiment Station, in a locality formerly occupied by the sage¬ 
brush association, have shown that none of the varieties of wheat, oats, 
barley, spelt, and emmer grown without irrigation under these conditions 
have tissue fluids with an osmotic concentration as high as that which 
at comparable seasons of the year characterizes the more permanent 
native species of the associations occurring at lower levels than the sage¬ 
brush. 7 
Crops other than the small grains have been investigated only under 
irrigation—an artificial condition obviously interfering with the use of 
indicator plants as a criterion in the selecting of land for crop production. 
As grown under irrigation, corn and the grain sorghums show osmotic 
concentration of the leaf-tissue fluids which are relatively low as compared 
with the native species discussed in this paper. 
Egyptian and Upland cotton when grown with irrigation under the 
more saline conditions of the Gila River Valley (22) have a much lower 
osmotic concentration of their leaf-tissue fluids than that of most of the 
plant species of the more saline regions of the Tooele Valley. 
The toxicity to agricultural plants of the salts present in the soil and 
the incapacity of agricultural plants for developing osmotic concentra¬ 
tions sufficiently high to enable them to withdraw water from the soil, 
must both be considered in seeking for the physiological explanation of 
the varying suitability of the various habitats for crop production. 
SUMMARY AND CONCLUSIONS 
The earlier studies of Kearney, Briggs, Shantz, McLane, and Piemeisel 
(24) have shown that in Tooele Valley, Utah, the plant associations of 
natural vegetation indicate the conditions of soil moisture and salinity 
of the land on which they are found and thus afford a basis for the esti¬ 
mation of its suitability for crop production. 
The purpose of the present investigation has been a consideration of 
the physicochemical properties of the leaf-tissue fluids of these indicator 
plants with a view to determining whether the magnitudes of such con¬ 
stants as osmotic concentration, specific electrical conductivity and 
chlorid content show a parallelism to the series of soil and vegetation 
types recognized by our predecessors in this field. 
The following salient facts concerning the vegetation may be noted. 
The statements concerning soils are based upon the findings of our 
7 Comparison of the crop plants with the herbaceous species of the several associations is precluded by 
the fact that most of the native herbs complete their development and disappear long before the winter 
grains reach maturity. 
