I FLORA OF THE DISTRICT OF COLUMBIA. 103 



6. Deweyanae Tuckerm. 

 Sometimes united with the following s^tion. 

 A single species 18. 0. bromoides. 



7. Elongatae Kunth. 



Spikes comparatively few -flowered; perigynia usually radiate or reflexed; stami- 

 I. nate flowers mostly below the pistillate. Closely allied species, growing usually in 

 wet woods, borders of ponds, or other locations where the soil is fairly moist throughout 

 the season. 



Perigynium broadest near the middle, conspicuously nerved; beak short and smooth. 



19. 0. rosaeoides. 

 Perigynium broadest near the base; beak serrulate. 

 Beak of perigynium half as long as the body, sharply toothed. Scales acutish to 

 acuminate. 

 Leaves 1 mm. wide or more, usually shorter than the culm; perigynia ovate. 



20. C. cephalantha. 

 Leaves less than 1 mm. wide, much longer than the culm; perigynia lanceolate. 



20a. C. angustior. 

 Beak of perigynium not more than one-third as long as the body, thin-toothed. 

 Scales usually acute to acuminate; beak of perigynium about one-third as long as 



the body 21. C. incomperta. 



Scales usually obtuse to slightly acute; beak of perigynium very short. 

 Leaves 1-2 mm. broad, shorter than the culm; perigynimn nearly or quite nerve- 

 less on the inner side 22. C. interior. 



Leaves narrower, usually much longer than the culm; perigynium strongly 

 nerved on the inner aide 23. C. howei. 



8. O vales Kunth. 



Spikes ovate, dense, usually tawny; perigynia wing-margined; staminate flowers 

 always below. Perhaps the most distinct section of the Vigneae, certainly the most 

 complex. 



Perigynia narrowly to broadly lanceolate, at least two and one-half times as long as 

 broad, much exceeding the scales. 

 Leaves at most 3 mm. wide, those of the sterile shoots few, ascending; spikes glossy 



brown or straw-colored, pointed 24. C. scoparia. 



Leaves wider, those of the sterile shoots very numerous, widely spreading; spikes 

 green or dull brown, blunt. 

 Tips of perigynia appressed or ascending; spikes 7-12 mm. long. 



25. C. tribuloides. 

 Tips of perigynia widely spreading or recurved; spikes 4-8 mm. long. 



Inflorescence flextious, elongate; culm weak, slender 26. C. projecta. 



Inflorescence compact, oblong; culm stiff 27. 0. cristatella. 



Perigynia narrowly ovate to suborbicular or obovate, not more than twice as long as 

 broad, often equaled or exceeded by the scales. 

 Perigynia 3-4 mm. long, nerveless or finely ner\'ed on the inner face. 

 Spikes gray-green when mature. Scales usually obtuse. ...28. C. albohitescens. 

 Spikes straw-colored or brownish when mature. 

 Hyaline portion of sheath very short; scales hyaline, with a conspicuous green 



stripe on each side of the midrib 29. C. straminea. 



Hyaline portion of sheath longer; scales tinged with reddish brown, without 

 green stripes 30. C. festucacea. 



