Mar. 22, 1924 
Tissue Fluids of Indicator Plants 
9 i 5 
DISCUSSION OF RESULTS 
Comparison among the various associations may be made in two ways, 
(a) by the comparison of the average values of the whole series of deter¬ 
minations made in the several associations and (b) by the comparison 
of constants based on one and the same species when growing in two 
different associations. 
Notwithstanding the very large number of determinations made 
in our field operations, a fully satisfactory comparison on either 
basis is not yet possible. Conditions of vital importance to the plant, 
such as soil moisture, soil salinity, temperature, insolation, and the 
evaporating power of the air, change rapidly with the march of the 
season. Thus two determinations on the same species in two different 
associations are not directly comparable unless synchronously made. 
The great labor of securing the samples and carrying out the measure¬ 
ments renders this ideal practically impossible of attainment. Thus the 
comparison here made must be regarded as tentative. 
COMPARISON OF THE VARIOUS ASSOCIATIONS OF TOOELE VALLEY AMONG 
THEMSELVES 
The averages of the various constants for the habitats discussed in 
the preceding pages appear in Table XIV. 
Considering first the mean values of freezing point lowering in degrees, 
A, and osmotic concentration in atmospheres, P, we may note first of 
all that in every instance the osmotic concentration of ligneous plants 
is higher than that of herbaceous plants. This result is in agreement 
with that derived from earlier studies in the more mesophytic region of 
Long Island, N. Y. (11), in the Jamaica Montane Rain Forest (17), and in 
the Arizona deserts ( 12 ). In the comparison of the various habitats we 
must, therefore, direct our attention to the two growth forms separately. 
It is clear that for the ligneous plants the osmotic concentration in 
the sagebrush association is higher than that in the Stansbury Mountains 
at higher levels. This is true whether we consider the three subdivisions 
of the sagebrush association separately or class all three together. 
The number of ligneous species from the sandhill mixed association 
is too small to justify a comparison between it and the sagebrush asso¬ 
ciation. The average of the three ligneous species is, however, higher 
than that of the ligneous plants of the Stansbury Mountains at higher 
elevations. 
The ligneous plants of the Kochia association show a higher osmotic 
concentration than that found in any of the foregoing habitats. 
The ligneous species in the shadscale association as a whole seem to 
show lower concentration than those of the sagebrush association. This 
is, however, due to the fact that most of the ligneous species recorded as 
occurring in the shadscale association are found in the washes where 
they doubtless have a much larger supply of water. The average of 
the determinations on the shadscale itself is 43.6 atmospheres, a value 
far higher than that of any of the preceding. Even higher values for 
the leaves of the shadscale have been demonstrated elsewhere and 
probably would be found here if determinations were made at the period 
of maximum dryness. 
