Mar. 22 , 1924 
Tissue Fluids of Indicator Plants 
899 
of the Kochia’ association, of the greasewood-shadscale association, or 
even, in places, of the salt flats. 
The upper limit of the association is far less definite, since sagebrush 
extends to considerable elevations and is an important element in the 
vegetation of the mountains. For the purpose of the present paper, we 
have taken the upper limit of the sagebrush association to be equivalent 
to the elevation at which cedars become an important element in the 
vegetation. 
In order to obtain a basis of comparison for the vegetation of the drier 
or more saline habitats, we have found it desirable to make a few deter¬ 
minations on species growing in the mouths of the canyons. We have, 
therefore, divided the sagebrush association into two parts for con¬ 
venience of treatment—the sagebrush association of the alluvial fans 
and the sagebrush association of the foothills canyons. 
Since the washes which are not occupied by permanent streams diver¬ 
sify the topography and soil conditions and afford moisture in greater 
quantities and for longer periods than do the relatively uniform and 
undiversified slopes of the alluvial fans, it has seemed desirable to divide 
the sagebrush association of the alluvial fans into two sections, one of 
which treats of the typical sagebrush association while the other deals 
with the vegetation of the generally dry watercourse or washes through 
the sagebrush association. 
On a priori grounds, one might expect that the osmotic concentration 
of the plants of the typical sagebrush association would be somewhat 
greater than that of those bordering the washes or of the stream beds, 
which are generally dry during the summer season, at the mouths of the 
canyons. 
Our predecessors (24) conclude that in Tooele Valley the soil condi¬ 
tions for a good stand and development of sagebrush are, (a) a rather 
coarse-textured soil readily permeable to water, with a small run-off and 
good underdrainage, (6) a depth of soil of at least 3 feet in which water 
can be stored and into which roots can penetrate, and (c) at least 3 feet 
of soil in which the salt content is very low. 
These conditions are best met on the upper outwash slopes and on the 
sand hills. Poorly developed plants of sagebrush may occur in other 
localities, as in the Kochia association, and even in the greasewood-shad¬ 
scale association, but in such localities the development is highly abnormal, 
and the tissue fluids may be characterized by very high concentrations. 
The determinations on the herbaceous species of the sagebrush asso¬ 
ciation were of necessity made chiefly during the early part of the season, 
since they are practically all of the ephemeral type. Most of these 
species develop with great rapidity in the early part of the season when 
the soil moisture has not yet been exhausted from the upper foot or two 
of soil. By early summer they have fruited and died down to the ground. 
They are, therefore, “drought evading” rather than “drought resisting” 
(23), corresponding in this regard to the winter annuals of the Arizona 
deserts. 
THE SAGEBRUSH ASSOCIATION OP THE FOOTHILLS CANYONS 
This division has been included largely as a means of securing a basis 
of comparison with the drier or more saline areas of the broad valley. 
It is perhaps misnamed, since the plants considered are practically 
entirely taken from the banks of the watercourses where sagebrush is not 
the dominant element in the vegetation. Sagebrush is, however, the 
chief ligneous plant on the slopes of the canyon walls. 
