78 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



8. GRAMINEAE. 15 Grass family 



Contributed by Jason R. Swallen 



Herbs (woody in Arundo) ; stems (culms) hollow or solid, closed at 

 the nodes; leaves 2-ranked, parallel-veined, composed of a sheath 

 enclosing the culm, and a blade, with a hairy or membranaceous 

 appendage (ligule) between them on the inside; flowers perfect or 

 sometimes unisexual, arranged in spikelets, these consisting of a 

 short axis (rachilla) and 2 to many 2-ranked bracts, the lower two 

 bracts (glumes) empty, the succeeding ones (lemmas) bearing in their 

 axils a single flower, and between the flower and the rachilla a 2-nerved 

 bract (palea), the lemma, palea, and included flower constituting the 

 floret; stamens 1 to 6; anthers 2-celled; pistil 1, with 2 (rarely 1 or 3) 

 styles, and usually plumose stigmas; spikelets mostly aggregate in 

 spikes or panicles at the ends of the main culms and branches. 



This very large family contains the most valuable of all plants used 

 by man, the cultivated cereals, such as wheat, barley, maize, and rice. 

 It also includes the most important forage plants, many of which, 

 notably bluegrass, timothy, and fescue, are extensively grown for 

 hay and pasturage. Nearly all grasses of temperate regions are eaten 

 by grazing animals, but some are more nutritious and palatable than 

 others. Some of the native grasses of Arizona, especially species of the 

 genera Bouteloua (grama) and Hilaria, are outstanding range plants 

 upon which the maintenance of the cattle and sheep industries of the 

 State is largely dependent. Seeds of many of the native species were 

 used as food by the Indians. The sod-forming habit of many grasses 

 makes them preeminent as soil binders. A few of the Arizona species, 

 including the native red sprangletop (Leptochloa Jiliformis) and the 

 introduced species, Johnsongrass (Sorghum halepense) and Bermuda 

 grass (Cynodon dactylon), are troublesome; weeds in cultivated lands. 

 The two latter, however, are of considerable forage value and Bermuda 

 grass, in the long hot summers of southern Arizona, is the only satis- 

 factory grass for lawns. Many people are allergic to the pollen of 

 grasses, one of the commonest causes of "hay fever. " Several species 

 are commonly cultivated as ornamentals, notably such large plants 

 as the giantreed (Arundo), pampasgrass (Cortaderia) , and silvergrass 

 (Miscanthus) . A tribe of large woody grasses, the bamboos, comprises 

 species of great utility, especially in eastern Asia, as substitutes 

 for timber in construction. Another grass of very great economic 

 importance is sugarcane (Saccharum officinarum). 



Key to the genera 



1. Spikelets in groups of 3 to 5, falling entire, sometimes enclosed in spiny burs: 

 Tribe Zoysieae, see also genus Cenckrus (2). 

 2. Spikelets in groups of 2 to 5, sessile on a short zigzag rachis, enclosed in small 

 spiny burs composed of the indurate second glumes of the 2 lower 



spikelets 46. Tragus. 



2. Spikelets in groups of 3, the central one perfect, the lateral spikelets stam- 



inate, not enclosed in burs (3). 



3. Rigid perennials; groups of spikelets erect on the stiff axis _ 47. Hilaria. 



3. Delicate annual; groups of spikelets nodding on one side of the very 



slender axis 48. Aegopogon. 



15 Reference: Hitchcock, A. S. manual of the grasses of the united states. U. S. Dept. Agr. 

 Misc. Pub. 200. 1935. 



