ATLAS OF AMERICAN AGRICULTURE, 
Figure 40.—Black grama, tobosa grass, and yucca. (Mesquite grass.) This grassland is either pure 
or has scattered plants of yucca, mesquite, or creosote bush. Moisture conditions are very adverse. The 
growth period commences after the summer rains and continues until checked by drought. Northwest 
of Hope, N. Mex. 
Figure 41.—Crowfoot and six-weeks grama grass. (Mesquite grass.) The appearance is that of a short 
crop of cereal. Growth is rapid and follows summer rains. The grass is soon cured in place by drought 
and forms excellent pasture. Santa Rita, N. Mex. 
This grassland may be subdivided as follows: 
Black grama. 
Crowfoot grama. 
Curly mesquite. 
Tobosa grass. 
Black grama (fig. 40).-—The most extensive commu¬ 
nity is that of the black grama ( Bouteloua eriopoda ). 
It seldom occurs as an unmixed grassland, but over 
its surface are usually scattered yucca ( Yucca elata ), 
mesquite, creosote bush, black brush, or cat’s claw. It 
occupies most of the sandy or gravelly slopes lying 
between the river bottoms and the foothills in New 
Mexico, and it is common in Texas and Arizona (fig. 
3). It does not form a close sod, but a relatively open 
grass cover. 
Crowfoot grama (fig. 41.)—In southeastern Arizona 
(fig. 3) crowfoot grama {Bouteloua ro throe Mi) char¬ 
acterizes the greater portion of the grassland. This 
plant is erect in growth, and it forms an even 
stand which during good years can often be 
cut for hay. It is often associated with other 
species of Bouteloua and Aristida. Areas 
occupied by this type are often free of 
shrubby growth, but for the most part the 
mesquite, cat’s claw, and chollas from the 
adjacent deserts occur on these grasslands. 
On eroded or overgrazed areas six-weeks 
needle-grass {Aristida adscensionisj and six- 
weeks grama {Bouteloua gristidoides) are 
prominent. Like black grama, the crowfoot 
grama is excellent forage. 
Curly mesquite. —Curly mesquite {Hilaria 
helangeri) forms a close sod grassland in 
southeastern Arizona, which resembles very 
closely the buffalo-grama sod of the high 
plains. It occurs over rolling country at 
rather high elevations and is often accom¬ 
panied at the upper elevations by scattered 
oaks {Quercus emoryi). This is excellent 
grazing land. In Texas this type is almost 
always marked by scattered trees of mesquite, 
opuntia and other plants. The grass cover is 
somewhat more mixed in this section and is 
often composed partly of buffalo grass {Bul- 
bilis dactyloides ) and a number of other 
grasses, chiefly species of Aristida and Bou¬ 
teloua. 
period of greatest growth. Portions of the area have 
a rainfall of less than 20 inches, but in the east it runs 
to as high as 30 inches. The evaporation rate is high. 
This savanna occurs in Texas south of the Red River 
and mostly south and east of the Plains border. (Figs. 
2 and 3.) It also extends over the lower southwest por¬ 
tion of the high plains in Texas, 
Two divisions may be recognized within the area 
here considered: The thorn-bush and mesquite-grass 
associes and the mesqufte and mesquite-grass associa¬ 
tion. In the western portion the mesquite trees are 
small, and there are many other small thorny trees and 
bushes which occur at intervals over an open grass 
cover. Much of the land is rough and broken and the 
vegetation partly in a developmental stage. This area 
may be designated the tliorn-bush and mesquite-grass 
associes. Farther east the rainfall is heavier, the trees 
larger, and the grass cover much denser. This type 
Tobosa grass .—Tobosa grass (Hilaria mutica ) oc¬ 
curs throughout the range of the desert grassland 
and marks the heavy or impervious soils, especially 
in depressions where drainage water stands after a 
rain. It occupies extensive areas at the bottoms 
Of the basins and in distribution can be separated with difficulty 
from the desert shrub. 
While green it is regarded as good forage, but the plants soon 
become dry and woody. False needle grass (Scleropogon 
brevifolius ) is often abundant in tobosa-grass areas. 
MESQUITE AND DESERT-GRASS (DESERT SAVANNA). 
This type consists of a short-grass cover over which 
are scattered small trees or thorn bushes. Both the 
beginning and the end of the growth period are usually 
determined by available moisture. Temperature plays 
almost no part in limiting the growth of the natural 
vegetation. The distribution of water throughout the 
season is somewhat similar to that in the desert region. 
The rainfall is relatively heavy, but the high tempera¬ 
tures and the high-saturation deficit of the air subject 
the plants to extreme drought conditions. There is a 
tendency over much of the area for the greatest rain¬ 
fall to come in the spring and summer, during the 
Figure 42.—A curly mesquite-grass sod with an occasional tree of mesquite and cholla. 
(Desert savanna.) This grassland in general aspect is somewhat similar to the short grass of the 
plains. The grasses subsist on the moisture stored in the surface soils, while the trees draw 
their moisture supply largely from the sub soil. The grasses are chiefly curly mesquite with 
aristidas and gramas. Big Springs, Tex. Photographed by A. J. Olmstead. 
tion occurring, in general, at a depth of 1\ to 2^ feet. 
Although the rainfall is relatively heavy, 20 to 30 
inches, it does not penetrate deeply into the soil and is 
rapidly absorbed and transpired by the growing plants. 
This association forms a band about 150 miles wide 
extending from the Gulf of Mexico on the south to 
the Red River on the north. This band in the cen¬ 
tral portion is bent westward to Martin County, Tex. 
The larger mesquite trees and much denser grass 
cover distinguish this association from the thorn-bush 
and mesquite-grass associes. This is because the 
available moisture is greater in the mesquite and mes¬ 
quite-grass area. On the north mesquite is apparently 
limited by low temperatures and on the east by the 
oak forests. Mesquite here grows on a dark soil with 
a layer of lime accumulation at about' 2| feet. The 
oaks grow on sandier land of lighter color where the 
zone of carbonate accumulation has disappeared. 
This area is suitable for grazing and the 
mesquite trees furnish both fence posts and 
firewood. Much of this land has been put 
under cultivation. Cotton is the principal 
crop, although grain sorghums are important, 
especially in the north, and corn throughout 
the area. 
Tliorn-bush and mesquite grass .—In the thorn- 
bush and mesquite grass associes thorn bushes and 
cacti, as well as mesquite, are scattered over a 
sparse desert-grass cover. The soil is always visible 
because of the sparse vegetation. 
The cover in this association is composed of curly 
mesquite grass (Hilaria belangeri), buffalo grass 
(Bulbilis dactyloides), species of Aristida, and other 
desert grasses. Small mesquite trees (Prosopius 
juliflora ) are scattered over this grass cover, and 
with these are associated thorn bushes and cacti of 
various types. 
This associes extends in a narrow strip from the 
Gulf of Mexico near the mouth of the Rio Grande 
River northwest to the southeast corner of New 
Mexico and across and up the southeast border of 
the high plains into Cottle and Motley Counties, Tex. 
On the western edge this type passes either into 
southern desert shrub, in which case the grasses dis¬ 
appear and a shrubby, open growth takes its place, 
or into desert grassland, in which case the trees and 
shrubs disappear, leaving the grasses dominant. 
The high water requirement in this hot climate 
and the long drought period make this type of doubt¬ 
ful agricultural value. Attempts have been made to 
grow cotton and grain sorghums in the better 
portions, 
may be distinguished as the mesquite and mesquite- 
grass association. 
Mesquite and mesquite grass (fig. 42).—Mesquite 
and mesquite grass constitute one of the most dis¬ 
tinctive types of Texas vegetation. The trees may 
be either scattered or close together to form an open 
forest. They often give the appearance of an orchard 
of small fruit trees. Mesquite {Prosopis juliflora ) is 
the dominant tree, although others occur. In many 
places, especially in the south, prickly pear {Opuntia 
lindhebneri) is almost as plentiful as mesquite. 
Grasses are abundant, chiefly curly mesquite {Hilaria 
belangeri) , buffalo grass {Bulbilis dactyloides ), and 
species of Aristida and Bouteloua. Mesquite is often 
damaged by drought. 
In general appearance this association suggests an 
abundant water supply, followed by extreme drought. 
The soil is not deep, the layer of carbonate accumula¬ 
MARSH GRASS (MARSH GRASSLAND). 
Marsh grassland occurs in scattered areas in 
many portions of the United States. The 
most important areas occur in the central valleys of 
California, along the Gulf and Atlantic coasts, and in 
the Everglades of Florida. (Figs. 2 and 3.) They may 
be classified roughly into salt marsh and fresh marsh. 
For the most part the salt marsh lies along the coast, 
although in Oregon and California the inland marshes 
are often developed in alkali areas and a sharp distinc¬ 
tion between salt and fresh marshes can not be made. 
The fresh marshes are characterized largely by Indian 
rice {Zizania aquatica and Z. palustris) , cat tail {Typha 
latifolia) , and tule {Scirpus valid us) (fig. 44), and in 
Florida by saw grass {Cladium, jamaicense) (fig. 43); 
while the salt marshes are marked by marsh grass 
{Spartina altemifolia and S. patens) along the coast. 
The principal places where marsh-grass lands have 
been used for agricultural purposes are in California, 
where the islands or deltas of the San Joaquin and the 
Sacramento have been diked off, drained, and made into 
