May 24 ,1924 Significance of the Southwestern Desert Vegetation 733 
Less Frequent or Rare 
Aristida adscensionis L. 
Brodiaea capitata pauciflora Torr. 
Baeria chrysostoma Fisch. & Mey. 
Calandrinia caulescens H. B. K. 
Chaenactis carphodinia A. Gray. 
Chaenactis stevioides Hook. & Arn. 
Chamaesyce polycarpa (Benth.) Millsp. 
Cryptanthe pterocarpa (Torr.) Greene. 
Monoptilon bellioides (A. Gray) Hall. 
Gilia inconspicua (J. E. Smith) Dougl. 
Lesquerella gordoni sessilis S. Wats. 
Linanthus dactylophyllus (Torr.) Rydh. 
Lotus sp. 
Lotus subpinnatus Lag. (?) 
Lotus strigosus (Nutt.) Greene. 
Lupinus concinnus Agardb. (?) 
Mentzelia albicaulis Dougl. 
Orthocarpus purpurascens Benth. 
Pachylophus (?) 
Phacelia crenulata Torr. 
Plantago erecta Morris. 
Salvia columbariae Benth. 
Silene antirrhina L. 
Sphaerostigma decorticans (Hook. & 
Arn.) Small. 
The soil conditions of the giant cactus and paloverde association at Chand¬ 
ler, Ariz., in 1915 are shown in Table V. 
Table V. —Soil conditions in giant cactus and paloverde association at Chandler , 
Ariz.. 1915 a 
Item 
Depth i 
of soil | 
! i 
i | 
1 
i \ 
| i 
Da 
March 28 
te of colleci 
Average 
tion 
October 5 
i 
Sample 6 
! No. 23 
Sample® 
No. 25 
Sample 
No. 23 
Sample 
No. 25 
.. ' ■' 1 . ... | 
| 
Feet ] 
Moisture equivalent. j 
1 f 
9.1 
17.8 
13.4 
17.6 
j 
2 ! 
8.3 
22.2 
15.3 
21.5 
3 
7.1 
23.6 
15.4 
26.5 
i 
4 ; 
6.9 
19.6 
13.2 
19.1 
! 
Wilting coefficient. ! 
1 ! 
6.0 
9. 7 
7.3 
9.6 
2 ! 
4.6 
12.0 
8.3 
11.7 
3 I 
3.9 
12.8 
8.4 
14.4 
4 i 
i 
3.8 
10.6 
7.2 
10.4 
Moisture content above or below wilting j 
i! 
-2.1 
+0.4 
-0.9 
-3.0 
coefficient. 
2 i 
-0.8 
+6.8 
+2.5 
-3.7 
3 1 
-0.6 
+6.9 
+2.7 
-6.6 
4 1 
j 
-0.2 
+6.7 
+3.3 
+0.5 
Salt content. 
1 ! 
.07 
. 11 
2 
.j 
. 10 
.09 
3 ! 
.17 
.14 
4 i 
! 
i 
.! 
.34 
. 26* 
a All data in this table are stated in percentages of the dry weight of the soil. 
b Taken in a typical area in the upper part of this association in a very stony soil near the hills. 
« Taken in the lower part of this association mired with desert-sage. 
CREOSOTE BUSH ASSOCIATION 
TOPOGRAPHICAL RELATIONS 
In the southwestern desert region the creosote bush association is the most 
important type of vegetation. It covers an area that includes the Mohave 
desert, Coachella Valley, Imperial Valley, Salt River Valley, Gila Valley, Death 
Valley, and most of the southern portion of New Mexico, Arizona, and the 
Transpecos region of western Texas. 
The creosote bush areas cover the high benches, the fans at the mouth of 
canyons, and strips of land lying at the base of the hills. Where the slope at 
