GENEKA OF GRASSES OF THE UNITED STATES. 113 



utilized for hay. Much of the grain hay of that region is made from 

 either cultivated or wild oats. 



The varieties of cultivated oat are derived from three species of 

 Avena. The common varieties of this country and of temperate and 

 mountain regions in general are derived from A. faitua. The 

 Algerian oat grown in North Africa and Italy and the red oat of our 

 Southern States are derived from A. sterUis. A few varieties 

 adapted to dry countries are derived from A. bar'bata'*-. 



Avena sterilis L., animated oats, is sometimes cultivated as a 

 curiosity. When laid on the hand or other moist surface the fruits 

 twist and untwist as they lose or absorb moisture. 



Our two native species, found in the Rocky Mountain region, are 

 perennials, with narrow few-flowered panicles of erect spikelets 

 smaller than those of Avena sativa. They are excellent forage 

 grasses, but occur only scatteredly. 



48. AREHENATHERUM Beauv. 



Spikelets 2-flowered, he lower floret staminate, the upper perfect, 

 the rachilla disarticulating above the glumes, produced beyond the 

 florets as a slender bristle ; glumes rather broad and papery, the first 

 1-nerved, the second a little longer than the first and about as long 

 as the spikelet, 3-nerved; lemmas 5-nerved, hairy on the callus, the 

 lower bearing near the base a twisted, geniculate, exserted awn, the 

 upper bearing a short, straight, slender awn just below the tip. 



Perennial, rather tall grasses, with- flat blades and rather dense 

 panicles. Species about six, in the temperate regions of Eurasia; 

 ' one species introduced into the United States. 



Type species : Arrhenatherum avenaceum Beauv. 



Arrhenatherum Beauv., Ess. Agrost. 55, pi. 11, f. 5. 1812. Beauvois figures 

 one species, which he calls Arrhenatherum avenaceum. This is Avena elatior 

 L., and is now called Arrhenatherum elatius (L.) Mert. and Koch. 



Arrhenatherum elatius (PI. XII; fig. 59) is occasionally cultivated 

 in the humid regions of the United States as a meadow grass under 

 the name of tall oat-grass. It is a fairly satisfactory forage grass, 

 but the seed is expensive and often of poor quality. This species is 

 often found growing spontaneously* in grassland and along road- 

 sides in the Northern States. 



A variety, Arrhenatherum elatius bulb o sum (Presl) Koch, has ap- 

 peared recently in some of the Atlantic States. It differs from the 

 ordinary form in having at the base of the stem a moniliform string 

 of 2 to 5 small corms 5 to 10 mm. in diameter. 



1 See Journ. Hered, 5 : 56, 1914, a translation of an article by Trabut. Also see Norton, 

 Amer. Breed. Assoc. 3: 281. 1907. 



97769 19 Bull. 772 8 



