May 24,1924 
Significance of the Southwestern Desert Vegetation 769 
VARIATIONS FROM THE TYPICAL COMMUNITY 
Chamiso 
In the Gila Valley (fig. 3) the chamiso ( Atriplex canescens (Pursh) Nutt.) covers 
long low narrow sandy ridges not at all like the high, wind-blown sand hills of 
the Coachella Valley. Here the half-buried abnormal growth of the mesquite is 
lacking. Chamiso is often the only shrubby species, though frequently there is 
found an Isocoma wrightii (A. Gray) Rydb. and, more rarely, Baccharis saro- 
throides A. Gray or Sphaeralcea coulteri A. Gray. The annuals are abundant 
(PL 11, A). Among them are some showy large-flowered species. 
The following list includes all the plants found in this community: 
PERENNIAL SPECIES OF CHAMISO 
Common or Frequent 
Atriplex canescens (Pursh) Nutt. Isocoma wrightii (A. Gray) Rydb. 
Prosopis glandulosa Torr. 
Less Frequent or Rare 
Baccharis sarothroides A. Gray. Sphaeralcea coulteri A. Gray. 
ANNUAL AND BIENNIAL SPECIES 
Common or Frequent 
Thelypodium lasiophyllum (Hook. & 
Arn.) Greene. 
Conanthus demissus (A. Gray) Heller. 
Pectocarya penicillata (Hook. & Arn.) 
A. DC. 
Baeria chrysostoma Fisch. & Mey. 
Fesiuca odoflora Walt. 
Anogra albicaulis (Pursh) Britton. 
Plantago ereda Morris. 
Pachylophus sp. 
Mentzelia albicaulis Dougl. 
Dipetalia subulata (Webb & Berth.) 
Kuntze. 
Machaer anther a parviflora A. Gray. 
Chylisma scapoidea (Nutt.) Small. 
Amsinckia menziesii (Lehm.) Nels. & 
Macbr. 
Less Frequent or Rare 
Eriogonum thurberi Torr. 
Erodium texanum A. Gray. 
Draba cuneifolia Nutt. 
Lappula occidentalis (S. Wats.) Greene. 
Eremalche exilis (A. Gray) Greene. 
Conanthus demissus (A. Gray) Heller. 
Matricaria matricarioides (Less.) Porter. 
Phacelia sp. 
Sophia glabra Woot. & Standi. 
Spermolepis echinatus (Nutt.) Heller. 
The moisture equivalents are low, especially in the upper 2 feet of soil (Table 
XXII). The moisture-holding capacity therefore is not high, but the penetra¬ 
tion is such that it is not likely that any water runs off during rainfall. Avail¬ 
able water was found in the first 4 feet of soil in March. In October, available 
water was present in a very small quantity in the fourth foot only. 
In three out of the four borings in this type of land the salt content was very 
low in all 4 feet. In one case (sample 13, Table XXII) the readings were much 
higher, especially below the first foot. There was considerable lime in small 
lumps scattered throughout the lower depths. From the standpoint of growing 
crops these quantities of salts would not be of great importance. 
Chamiso (“sand bars”) in the Gila Valley indicates (1) a light sandy soil; 
(2) soil moisture available in spring in all 4 feet of soil; and (3) a low salt content. 
These areas are not extensive enough to be of great importance agriculturally. 
However, they can be farmed. In some cases they have been leveled and used 
for truck crops. 
