912 
Journal of Agricultural Research 
Vol. XXVII, No. 12 
Table XI gives the constants for the sap properties of the grasses. 
Sporoboeus airoides Torr. —The first determination of July 27 was 
made on material taken in Tooele Valley. The sample of June 28 was 
taken on the small sand dunes southeast of Pavant Butte in -the Sevier 
Desert. This species also occupies low depressions on the leeward side 
of sand dunes on the eastern edge of the sterile portions of the Great 
Salt Lake Desert at Knolls, where it was taken on July 17. 
Disticheis spicata (L.) Greene. —It is not known just how large a 
concentration of soil solution D. spicata will tolerate. Kearney and his 
associates noted that the salt concentration is higher in the soil under the 
salt-grass community than under that occupied by the Sporobolus- Chry- 
sothamnus community. The writers’ notes show that where the drainage 
water from the thermal springs at the northern end of the Stansbury 
Mountains is abundant, D. spicata and Salicornia utahensis occur in 
association. A reading on the water indicates an osmotic concentration 
of about 21.6 atmospheres and a conductivity of 0.046 mho. 
For actual determinations on the tissue fluids of DisticKlis spicata we 
must turn to collections made elsewhere than in Tooele Valley. A sample 
was taken on the low grounds east of the Ice Spring Craters lava field, 
Sevier Desert, on July. 5. 
At the bottom of the Terrace Crater, Ice Spring Craters, Sevier Desert, 
is a small plot of grass which has apparently remained in about its present 
condition since it was first noted by the geologists of the Wheeler survey. 
It is a pure stand of DisticJilis spicata . The plot is not much higher than 
the level of the ground water in the ancient lava vent, which has been 
shown to be rather saline ( 8 ). The sample taken at midday on July 5 (the 
second sample of that date) was possibly slightly wilted and with a trace 
of excreted salt on the surface of the leaves. Repetition of this col¬ 
lection on July 20, 1921, gave somewhat lower values. 
These determinations indicate a rather high concentration, including 
an abundance of chlorids, in the leaf-tissue fluids of the salt grass when 
growing in its typical halophytic habitats. When growing where salts 
are less abundant, as on the sandy plain which represents a portion of 
the ancient delta of the Sevier River (sample of June 29), the plant shows 
a much lower concentration. 
The values for osmotic concentration and electrical conductivity are 
only about half as large as those which were found when the species was 
growing in highly saline areas. The chlorid content is only about one- 
fourth as high. One of these lacks a conductivity measurement. That 
Distichlis spicata has an inherently higher concentration than some other 
grass species, and that the concentration is not determined solely by 
the environment is shown by comparison with determinations made on 
Hilaria jamesii with which it was immediately associated, (June 20), on 
the ancient delta of the Sevier River. We may note that H. jamesii 
contains only about half the chlorids found in D. spicata in association 
with it. 
SALT-FLAT COMMUNITIES 
The most highly saline conditions of the region are encountered in the 
great mud flats which cover an area of many square miles along the 
southern shore of the Great Salt Lake. These flats are diversified by 
low ridges, which have already been considered in the discussion of the 
greasewood-shadscale association. The flats are so gently sloping that 
they appear level. In drier periods the grit of salt can be felt as one 
