FLORA OF THE DISTRICT OF COLUMBIA. 81 



13. ZIZANIA L. 

 1. Zizania palustris L. Wild rice. 



In shallow water, covering extensive areas in the marshas along the Eastern Branch, 

 bordering Analostan Island, and elsewhere along the Potomac; rarely growing in 

 pockets of wet soil among rocks on islands. July-Sept. Eastern and middle states. 

 (Z. aquatica of Ward's Flora.) 



The plants are annuals, though the large size and pure stands give the impression of 

 a perennial. Also called Indian rice and water rice. Plate 13 shows this as it grows 

 in Eastern Branch in summer. 



14. HOMALOCENCHRTJS Mieg. 



Spikelets 2.5-3 mm. long; branches single, nearly straight, spikelet-bearing toward 

 the end 1. H, virginicus. 



Spikelets 4-5 mm. long; lower branches clustered, spikelet-bearing from below the 

 middle 2. H. oryzoides. 



1. Homalocenclirus virginicus (Willd.) Britton. White grass. 

 Swampy woods and copses. Aug.-Sept. Eastern U. S. {Leersia virginica Willd.) 



2. Komalocenchrus oryzoides (L.) Poll. Rice cut-grass. 

 Wet open ground, along streams, and in railroad ditches; common. Sept. Through- 

 out the U. S.; also in Eur. and Asia. {Leersia oryzoides L.) 



15. PHALARIS L. 



Plants annual; heads ovate; glumes wing-keeled 1. P. canariensis. 



Plants perennial; panicle 6-15 cm. long, open during anthesis; glumes not wing- 

 keeled 2. P. arundinacea. 



1. Pialaris canariensis L. Canary grass. 

 Waste ground; an infrequent escape from cultivation. May-June. Atlantic and 



Pacific Coast states; introduced from Eur. 



2. Phalaris arundinacea L. Reed canary grass. 

 Wet ground or in shallow water; frequent. June. Northern states, south to Md.; 



also in Eur. and Asia. 



In past years popular as an ornamental, especially the form called ribbon grass, 

 with blades striped with white (var. picta L.). 



16. ANTHOXANTHUM L. 



1. Anthoxantlium odoratum L. . Sweet vernal grass. 



Meadows, lawns, old fields, and open woods; common everywhere. May. Atlantic 

 and Pacific Coast states; naturalized from Eur. 



17. ARISTIDA L. Needle grass. 



Plants perennial, 30-60 cm. tall; spikelets crowded on the short erect branches of a 



narrow panicle 1. A. purpurascens. 



Plants annual; spikelets not crowded, the panicle nearly simple. 



Middle awn coiled at base at maturity 2. A. dichotoma. 



Middle awn not coiled. 



Lateral awns 2-6 mm. long, much shorter than the middle one 3. A. gracilis. 



Lateral awns 3.5-7 cm. long, about as long as the middle one 4. A. oligantha. 



1. Aristida purpurascens Poir. 



Sterile woods and rocky banks of rivers; frequent. Eastern U. S. 

 All the species of Aristida flower in late summer and autumn. 

 69289—19 6 



