2 3 8 



GRAMINEAE. 



Vol. I. 



79. RHOMBOLYTRUM Link, Hort. Berol. 2: 296. 1823. 



Perennial grasses, with usually flat leaf-blades, and a narrow contracted spike-like 

 panicle. Spikelets numerous. Scales several, the outer 2 empty ones i-nerved, the flowering 

 scales broad, rounded at the apex, 3-nerved, the nerves glabrous, the lateral ones vanishing 

 below the margin, the midnerve at the margin or sometimes excurrent as a short tip, the 

 callus pilose; palet 2-keeled. Stamens 3. Styles short, distinct. Stigmas plumose. Grain 

 free, enclosed in the scale. [Greek, in reference to the round flowering scales.] 



Species 4 or 5, natives of warm countries. Type species : Rhombolytrum rhomboideum Link. 



i. Rhombolytrum albescens (Vasey) Nash. 

 White Prairie-grass. Fig. 571. 



Triodia albescens Vasey, Bull. U. S. Dept. Agric. Div. 



Bot. 12 : Part 2, 33. 1891. 

 Sieglingia albescens Kuntze ; L. H. Dewey, Contr. U. S. 



Nat. Herb. 2: 538. 1894. 

 R. albescens Nash, in Britt. Man. 129. 1901. 



Culms tufted, erect, smooth and glabrous, i2'-2o' 

 tall, the sterile shoots one-half as long as the culm 

 or more. Sheaths shorter than the internodes, 

 smooth ; ligule a ring of short hairs ; blades smooth 

 beneath, roughish above, acuminate, 2i'-n' long, 

 1 "-2" wide; panicle dense and contracted, white, 

 2i'-s' long, i'-i' broad, its branches erect or ascend- 

 ing, 1' or less long; spikelets about 7-1 1 -flowered, 

 2"-2i" long, the empty scales white, I-nerved, about 

 equal; flowering scales about ii" long, 3-nerved, the 

 lateral nerves vanishing below the apex, all the 

 nerves glabrous, the midnerve excurrent in a short 

 scabrcTus point, denticulate and irregularly and ob- 

 scurely lobed at the truncate apex. 



Prairies, Kansas to New Mexico and Texas. Aug.-Sept. 



80. ERAGROSTIS Beauv. Agrost. 70. pi. 14. f. 11. 1812. 



Annual or perennial grasses, rarely dioecious, from a few inches to several feet in height, 

 the spikelets in contracted or open panicles. Spikelets 2-many-flowered, more or less flat- 

 tened. Two lower scales empty, unequal, shorter than the flowering ones, keeled, i-nerved, 

 or the second 3-nerved; flowering scales membranous, keeled, 3-nerved; palets shorter than 

 the scales, prominently 2-nerved or 2-keeled, usually persisting on the rachilla after the fruit- 

 ing scale has fallen. Stamens 2 or 3. Styles distinct, short. Stigmas plumose. Grain free, 

 loosely enclosed in the scale and palet. [Greek, signifying probably a Love-grass.] 



A genus of about 120 species, widely distributed throughout all warm and temperate countries. 

 Besides the following, some 15 others occur in the southern and western parts of North America. 

 Type species : Briza Eragrostis L. 

 Culms not creeping ; plants with perfect flowers. 

 Annuals. 



Spikelets 2-5-flowered, i"-iJ4" long. 



Culms branched only at base ; pedicels and branches of panicle long and capillary. 

 Flowering scales i',i"-iyi" long; culms rarely over 20', slender. 1. E. capillaris. 

 Flowering scales 2 , '-2j'i" long; culms 2° tall or more, usually stout. 2. E. hirsuta. 



Culms branched above the base ; pedicels and branches of the panicle short. 3. E. Frankii. 

 Spikelets 5-many-flowered, i}4"-8" long. 

 Spikelets 34" wide or less. 



Flowering scales thin, usually bright purplish, the lateral nerves faint or wanting; 



spikelets about 'A" wide. 4. E.pilosa. 



Flowering scales firm, usually dull purple or green, the lateral nerves very prominent ; 

 spikelets about J4" wide. 5. E. Purshii. 



Spikelets 1" wide or more. 



Lower flowering scales about 34" long; spikelets 1" wide. 6. E. Eragrostis. 



Lower flowering scales i"-iJ4" long; spikelets iJ4"— ij4" widd 7. E. major. 

 Perennials. 



Spikelets not clustered. 



Branches of the open panicle stiff, widely spreading, at least when old. 



Pedicels long, commonly at least the length of the spikelets. 8. E. pectinacea. 

 Pedicels commonly much shorter than the spikelets. 



Blades elongated ; branches of the panicle long and slender ; spikelets scattered, 



6-25-flowered. 9. E. refracta. 



Blades not elongated ; branches of the panicle short and stout, rigid, the spikelets 

 crowded, 5-12-flowered. 10. E. curtipedicellata. 



Branches of the elongated panicle erect or ascending, capillary. n. E. trichodes. 

 Spikelets clustered on the very short erect or ascending branches. 

 Culms extensively creeping ; plants dioecious. 

 Flowering scales less than 1" long, glabrous. 

 Flowering scales i^"-2" long, pubescent. 



12. E. secundiflora. 



13. E. hypnoides. 



14. E. Weigeltiana. 



