306 ANNUAL REPORT SMITHSONIAN INSTITUTION, 193 4 



However, certain species, especially the so-called " climbing bam- 

 boos ", reach up through the foliage of trees much as do some kinds 

 of brambles. The stems are prevented from slipping back by rather 

 stiff horizontal or reflexed branches. 



The grass family is adapted to a great variety of soils. The species 

 are found in salt- and fresh-water marshes, and in sand, as already 

 described, on rocks, and even in alkali wastes. 



The ordinary meadow grasses grow on moderately dry soil, receiv- 

 ing a medium rainfall. Here grow our familiar cultivated species, 

 Kentucky bluegrass {Poa pratenms) , redtop {Agrostis aJha), timothy 

 {Phhu7n pratense), orchard grass {Dactylis glomepata)^ meadow 

 fescue {Festuca elatior), Bermuda grass {Gynodon dactyl on) ^ and 

 others. The species may be sod-formers (with rhizomes) or bunch 

 grasses (without rhizomes). Of those mentioned above, Kentucky 

 bluegrass, redtop, and Bermuda grass have rhizomes; the others do 

 not. 



DISTRIBUTION 



The distribution of grasses in the United States depends largely 

 upon rainfall and temperature. The region from the Atlantic Coast 

 to eastern Nebraska and Texas usually receives sufficient rainfall to 

 produce staple crops, such as corn, wheat, and cotton, and the common 

 meadow and pasture grasses, such as timothy and bluegrass in the 

 North and Bermuda grass in the South. In a general way this area 

 is called the humid region. There is another humid region in the 

 northwestern States from northern California (west of the Sierras) 

 to British Columbia, and east to the Cascades. There are also many 

 small humid valleys in all the western mountain ranges. 



Much of the humid region in the East was originally covered with 

 forest. But in the northern and western part there were more or less 

 extensive grasslands called prairies. For example, much of northern 

 Illinois and Iowa was prairie, and the western fringe of the humid 

 region passed gradually from prairie to the vast treeless expanse of 

 the Great Plains. 



The wild grasses of the prairie are rather tall species, partly 

 rhizomatous, partly bunch grasses, such as blue joint turkeyfoot, some- 

 times called bluestem {Andropogon furcatus')^ prairie beardgrass or 

 little bluestem {A. scoparius), Indian grass {Sorghastrum nwtans), 

 and switchgrass {Panicuin vlrgatum) . 



The region between the Mississippi River and the Rockj^ Moun- 

 tains becomes increasingly dry toward the west. This, the Great 

 Plains, is a dry, nearly level area, increasing in altitude from 1,000 

 feet to about 6,000 feet at the foot of the mountains. The approxi- 

 mate line of demarkation between the prairie region and the Great 



