CYPEKACEAE (SEDGE FAMILY) 



187 



271. F. laxa. 



Var. pub6rula (Michx.) Britton. Leaves and scapes 

 pubescent. Ga. and Fla. to Tex. ; also n. in the flat country 

 to Ind., 111., and Mo. 



3. F. laxa Vahl. Culms slender (0.5-7 dm. high) from 

 an annual root, weak, grooved and flattish ; leaves linear, 

 flat, ciliate-denticulate, glaucous, sometimes hairy; spike- 

 lets ovoid, acute (0.4-1 cm. long) ; stamen 1 ; 

 achene conspicuously 6-S-ribbed on each side, 

 and with finer cross-lines. Low ground, near 

 the coast, Pa. to Fla and Tex. ; n. in the flat 

 country to 111. and Mo. July-Oct. (Trop. 

 Am.) FIG. 271. 



->- *- Spikelets glomerulate ; style glabrous. 



4. F. Vahlii (Lam.) Link. Dwarf tufted annual (0.3-2 dm. 



high); the culms, leaves and very elongated upright bracts fill- 

 272 F. Vahlii. form; glomerule 0.3-1 cm. in diameter; spikelets 3-8, sub- 



cylindric, greenish or pale brown, the narrow scales acuminate ; 

 achene minute, transversely reticulate. Damp sands, 

 etc., N. C. to Fla., Tex., and Mo.; introd. near Phila. 

 July-Oct. FIG. 272. 



* * tttyle 3-cleft ; achene triangular. 



5. F. autumnalis (L.) R. & S. Annual (1-4 dm. 

 high), in tufts; culms flat, slender, diffuse or erect \ 

 leaves flat, acute ; umbel compound or decompound, the 

 very numerous slender-cylindric to fusiform brown spike- 

 lets 4-10 mm. long ; the rnucronate-acuminate ovate- 

 lanceolate scales appressed stamens 1-3; achenes very 

 minute, 0.5 mm. long, smooth or 

 minutely roughened. Low grounds, 

 Pa., 111., and Mo., southw. July- 

 Sept. (Trop. Am.) FIG. 273. 



6. F. Frdnkii Steud. Similar, 



0.1-2 dm. high ; the umbel simple or slightly compound 

 (or the spikelets solitary in dwarf plants); spikelets ellip- 

 soid or narrowly ovoid, castaneous, the slender tips of the 

 scales slightly spreading; achenes 0.75 mm. long. (F. 

 autumnalis Man. ed. 6, in part.) Sandy shores, Me. to 

 274. F. Frankii. Ont., and south w. Aug.-Oct. FIG. 274. 



273. F. autumnalis. 



9. SCIRPUS [Tourn.] L. BULRUSH OR CLUB RUSH 



SpikeleCs few-many-flowered, solitary or in a terminal cluster when it is sub- 

 tended by a 1-several-leaved involucre (this when simple often appearing like a 

 continuation of the culm); the scales in several ranks, or rarely inclining to be 

 2-ranked. Flowers to all the scales, or to all but one or two of the lowest, all 

 perfect. Perianth of 1-6 (or 8) bristles, or sometimes wanting. Stamens 2 or 

 3. Style 2-3-cleft, simple, wholly deciduous, or sometimes leaving a tip or 

 point to the lenticular or triangular achene. Culms sheathed at base. (The 

 Latin name of the bulrush.) 



a. Involucre none, or merely the modified outer caducous scale of the soli- 

 tary terminal small (2.5-7 mm. long) spikelet ; achene trigonous, 

 smooth b. 

 b. Perianth-bristles terete and setulose. 



Scales of the flattened spikelet membranous and awnless ; bristles 



retrorsely barbed ; achenes beaked. 



Achene 1 mm. long, constricted below the beak . . . 1. /S. nanus. 



Achene 2-2.5 mm. long, the pale beak continuous with the body 2. S. pauciflorus. 

 Scales of the terete spikelet with firm green midribs, that of the 

 outermost prolonged into a blunt awn ; bristles setulose with 

 spreading or ascending fine hairs ; achenes beakless. 



