Mar. 22, 1924 
Tissue Fluids of Indicator Plants 
917 
The ligneous plants of the greasewood-shadscale association, the grass- 
flat communities and the salt-flat communities average 32 to 38 atmos¬ 
pheres. These figures, which must be regarded as approximate merely, 
show that the osmotic concentration found in the native vegetation of 
these habitats is far higher than that which is found in the tissue fluids 
of cultivated plants. Thus the physicochemical characteristics of the 
tissue fluids of the native vegetation are such as to indicate that few if 
any cultivated plants have osmotic concentration in their tissue fluids 
which would suit them for prolonged growth in such an environment 
as that presented by the shadscale association, the greasewood-shadscale 
association, the grass-flat, and the salt-flat communities as they exist 
in Tooele Valley. This does not necessarily imply that such habitats 
could not be suited for crop growth by proper irrigation under con¬ 
ditions permitting the removal of the salts from the soil by leeching 
and drainage. 
Comparing the mean values of specific electrical conductivity in 
ligneous and herbaceous plants, it appears that in every unit of classi¬ 
fication except the Stansbury Mountains at higher altitudes and the 
sagebrush association of the foothills canyons, the conductivity is higher 
in the ligneous than in the herbaceous plants. 
This result is in apparent disagreement with the findings of an earlier 
paper (20) in which it was shown that the specific electrical conductivity 
of ligneous plants is lower than that of herbaceous forms. 
It must be remembered, however, that in the , desert proper we are 
comparing herbaceous species of a very ephemeral nature with ligneous 
species which, to a greater or less extent, remain active throughout the 
season. Many of the latter are typical halophytes. Thus it might be 
expected that the ligneous plants would absorb^ and retain in solution 
larger quantities of salts than the herbaceous forms. 
In the Stansbury Mountains at higher elevations and in the sagebrush 
association of the foothills canyons where the conditions are more meso- 
phytic the conductivity of herbaceous plants is higher than that of 
ligneous plants, just as has been found to be the case in determinations 
made on Long Island. 
The average value of the ratio of specific electrical conductivity to 
freezing point depression K/A is higher in herbaceous than in ligneous 
plants in all the units of classification of the vegetation, with the 
exception of the constants based on the wholly inadequate series of 
determinations on herbaceous species in the Kochia association and in 
the salt flats. This result is in full agreement with the writers’ earlier 
findings. 
Turning back to the osmotic concentrations of the herbaceous species, 
it is clear that there is considerable irregularity in the values for the as¬ 
sociations higher than the grass flats and the salt flats. It is difficult to 
be certain of the same graduation in the magnitudes of osmotic con¬ 
centration as has been demonstrated for the ligneous species. It must 
not be forgotten, however, that we are here dealing largely with ephemeral 
species, which die down before the conditions become very severe. The 
average osmotic concentrations for the grass flats and salt flats are con¬ 
spicuously higher than those found in the other associations. 
The chlorid content of* the species of the greasewood-shadscale as¬ 
sociation, of the grass-flat communities, and of the salt flats is con¬ 
spicuously higher than that of any other habitat. The series of analyses 
is not sufficiently large to render further discussion desirable at this time. 
