May 24,1924 Significance of the Southwestern Desert Vegetation 
763 
Table XVIII.— Comparison of spring and fall soil conditions at the same stations 
in typical areas of saltgrass, Indio , Calif., 1915 a 
Date of collection 
Date of collection 
Item 
Depth of 
soil 
Mar. 5, 
sample 
No. 21 
Mar. 5, 
sample 
No. 22 
Average 
Sept. 22, 
sample 
No. 21 
j Sept. 22, 
1 sample 
No. 22 
Average 
Moisture equivalent. 
Feet 
1 
27.1 
27.1 
27.1 
23.5 
35.8 
29.7 
2 
14.9 
27.6 
21.3 
13.8 
26.7 
20.3 
3 
36.7 
34.2 
35.5 
29.0 
31.2 
30.1 
4 
16.4 
28.6 
22.5 
13.7 
28.2 
21.0 
W ilting coefficient... 
1 
14.7 
14.7 
14.7 
12,8 
19.5 
16.2 
2 
8.1 
15.0 
11.6 
7.5 
14.5 
11.0 
3 
20.0 
18.6 
19.3 
15.8 
17.0 
16.4 
4 
8.9 
15.6 
12.3 
7.4 
15.3 
11.4 
Moisture content above or be- 
1 
+18.3 
+14.2 
+16.3 
+10.1 
+0.7 
+5.4 
low wilting coefficient. 
2 
+22.2 
+12.6 
+17.4 
+13.7 
+5.8 
+9.8 
3 
+16.8 
+17.3 
+17.1 
+18.0 
+10.5 
+ 14.3 
4 
+24.6 
+14.1 
+19.4 
+19.4 
+16.0 
+17.7 
Salt content. 
1 
>2.60 
2.40 
2. 45 
>2.50 
1.66 
2.08 
2 
2.24 
.30 
1.27 
1.90 
.74 
1.32 
3 
.41 
.30 
.36 
1.16 
.89 
1.03 
4 
.26 
.13 
.20 
.47 
.58 
.53 
° All data in percentages of the dry weight of the soil. 
WASHINGTON PALMS 
TOPOGRAPHICAL RELATIONS 
The Washington palm is peculiar to Coachella Valley. The palms occur as 
scattered groups around springs or streams. The most of these are in the part 
of the valley above Indio, although in groups of two or three they extend down 
beyond Mecca. The most striking groups are those north of Indio where the 
palms make extensive groves just next to the barren clay hills (PI. 9). Large 
groups are also found above Palm Springs where the palms follow the mountain 
streams for several miles. 
BOTANICAL COMPOSITION 
Where the palm trees ( Washingtonia filifera Wendl.) grow around springs in 
the heavier soils there is usually a sod of Distichlis spicata (L.) Greene. In the 
group north of Indio Juncus robustus S. Wats, and Imperata hookerii Rupr. are 
associated with the Distichlis. On the lower places the Distichlis is mixed with 
J uncus cooperi Engelm. and Scirpus olneyi A. Gray. Along the streams in the 
hills the soil is rockier and the vegetation growing with the palms is charac¬ 
teristic of the washes, previously discussed under the Yucca and cactus association. 
APPEARANCE 
Because of the height and the contrast with the low, shrubby vegetation 
surrounding them, the palm groups make a striking appearance and can be 
seen for long distances. This is not true of the one or two trees often found 
at the springs in the flats, where scattered mesquite trees tend to hide the palms. 
The trees are often 50 feet or more in height, with a trunk about 2 feet in diam¬ 
eter. At the end of the growing season the leaves merely droop and dry but 
do not fall off, so that the upper part of the trunk is entirely hidden by the mass 
of old leaves (PI. 9). 
PHYSICAL CONDITIONS INDICATED 
Soil Moisture 
These palm groups always indicate a good supply of moisture either from 
springs or mountain streams available all the year. 
