344 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
The drawings accompanying this paper were prepared by Mrs. 
Agnes Chase, to whom the writer is indebted for numerous notes upon 
the minute structural details of the species. The half tones, except 
plate 69, are from photographs taken by himself, and now the prop- 
erty of the United States Department of Agriculture. 
ECONOMIC IMPORTANCE OF THE GRAMA GRASSES. 
It is doubtful whether there is another group of native pasture 
grasses which is of as much economic importance as this, when 
both quality and quantity are considered. In the northern prairie 
region Bouteloua gracilis forms a very large part of the so-called 
‘‘buffalo-grass formations,’’ and makes a very fair sod over thousands 
of square miles. The arable lands upon which this species forms a 
good turf, however, are rapidly being broken up and devoted to 
ordinary farm crops, so that in the north the areas of grama have 
been very much reduced in the last 20 years. 
In the arid Southwest, where the species are not turf formers, 
except at an altitude of 5,000 to 7,000 feet, the grama grasses are 
nevertheless of great importance, including, as they do, species which 
not only inhabit this region, but which actually furnish the greater 
part of the feed at altitudes from 7,000 feet down to the driest desert, 
mesas and lowlands. It is a noteworthy fact that the species which 
produce not only the greatest amount of feed, but the best feed 
as well, occupy the higher levels. This is of course accounted for by 
the heavier precipitation. 
The conditions upon the highland of Mexico are very much the same 
as in the southwestern part of the United States, the high tablelands 
being imperfectly sodded with Bouteloua gracilis, B. chondrosioides, 
B. fluformis, B. radicosa, B. hirsuta, etc., and the lower levels pro- 
ducing varying growths of such species as B. barbata and B. aristi- 
doides. The first group especially includes the main pasture grasses 
over very large areas. 
The species are preeminently pasture grasses and have been so 
recognized since they were first studied. Lagasca called attention 
to them in a very positive fashion as early as 1805, and our early 
explorers were unstinting in their praises of the gramas. It not infre- 
quently occurs, however, that many of the species enter quite largely 
into the composition of hay. Upon the prairies of the North Central 
States B. gracilis, formerly to a much greater extent than at present, 
was extensively cut with Agropyron smithii, Koeleria, and other 
prairie species. Farther south, in Nebraska, Kansas, Oklahoma, and 
northeastern New Mexico, B. curtipendula is more conspicuous, and 
B. hirsuta is also of some importance mixed with various species of 
Andropogon on sandy-loam soils. The most valuable species, how- 
ever, aside from B. curtipendula, do not well adapt themselves to 
