I. Stigmas 2. - Achenium double convex.

1 C. capitata L. Spike capitate or nearly globous, at the summit; fr. (perigynium) roundish-ovate, close compressed, convex-concave, glabrous, acutish, longer than the ovate and rather obtuse glume; lvs. slender. - Heights of the White Mts. (Robbins).

2 C. gynocrates Wormesk. Spike oblong, rather loose-flowered; perigynium suboval or oblong, tapering at base, veined, convex-terete, attenuate above into a terete, shortish, straight or subrecurved, bidentate beak, nearly horizontal in maturity, longer than the ovate and acute glume; culm slender, 4 to 6' high, with long slender leaves sheathing at base. Wayne Co., N. Y. (Sartwell), N. to Greenland. (C. Davalliana, 2d edit.)

3 C. exilis Dew. (Boott, Illust., No. 45.) Spike terminal, ovate or oblong close flowered, stamiuate below, sometimes a single spike or a single 3 spike i perig. ovate-lanceolate, convex above and slightly below, serrulate on the margin, ■minutely veined above, 2-toothed, diverging, some longer than the ovate-lanceolate glume; culm 12 to 20' high, stiffly erect, and lvs. setaceous. - Swamps, E. Mass. (Oakcs), Sandford Lake, N. Y. (Sartwell)'.

β. asdrogyna. One or more short spikes below the terminal. - Manchester, N. Y. (Kneiskern).

4 C. sterilis Willd. (Boott, lllus.. No. 135.) Spike compound, below, often dioecious; spikelets 4 - 6, ovate, subapproximate; perig. ovate, acuminate or sub-rostrate, bifid, compressed, triquetrous, scabrous on the margin, equaling the ovate, acutish glume; st. 2f high, erect and .stiff. Wet places, common. (C. stellulata β. sterilis Torn, Carey.)

5 C. bromoides Schk. Spikelets numerous, alternate, below, sometimes all ; perig. lanceolate, erect, acuminate, scabrous, nerved, bifid, twite longer than the ovate-lanceolate glume. - Common in small bogs, in wet places.

6 C siccata Dew. (Boott, Illust., No. 50.) Spikelets numerous, above, often wholly , ovate, close or approximate; perig. ovate, lanceolate, acuminate, compressed, nerved, bifid, scabrous on the margin, equaling the ovate, lanceolate glume. - Sandy plains, Westfield, Mass. (Davis); Ipswich, Mass. (Oakes); widely spread over the country, but not abundant, W. to I11.

7 C. Sartwellii Dew. Spikelets 12 - 20, ovate, sesxiile, compact, bracteate, lower •ones especially fructiferous; upper often at apex, sometimes wholly ; perig. urate, lanceolate, convexo-concave, subidate, slightly 2-toothed, margined and scabrous on the edge, a little longer than the ovate and acute glume; lvs. flat, linear, shorter than the stem. - Junius, Seneca Co., N. Y. (Sartwell).

'8. C. distycha Huds. Spikelets many, 2-roived or compressed into a flattened, compound, loose spike; spikelets oblong-ovate, close, alternate, often branched below and the lowest sometimes remote, upper and lower often , and the intermediate wholly , or from the middle wholly upwards; perig. ovale, narrow-rostrate, margin serrulate, narrow, equaling the ovate, acute glume: culm erect, leafy below. - Wis. (Lapham), I11. (Vasey), Mich. (Cooley), N. to Arc. Am. (C. intermedia Good.)

9. C. decomposita Muhl. (Boott, Illust., 53.) Spike decompound or paniculate; spikelets very many, ovate, alternate; perig. ovate, convex on both sides, triangular, acutish or short rostrate, short, brownish, glabrous, larger than the ovate, acuminate, whitish glume; st. 18 - 30' high. - Found in swamps, Michigan, and in Yate3 Co., N. York (Sartwell).

10 C prairea Dew. Spike below branched; spikelets ovate, sessile, 5 to 7 on a branch; perig. ovate-lanceolate, convex both sides, scabrous on the margin, slightly bind, smaller than the ovate-lanceolate glume; st. 2 - 3f high, leafy towards the base. - Abundant in the prairies of Michigan, and sparingly found in N. England and N. Y. Resembles C. paniculata L., which has a much broader ovate glume shorter than the perigynium and is far more paniculate, and for which this has been taken. From No. 24 it is far separated by its panicle, and the color and shape of its fruit.

11 C. cephalophora Willd. Spikelets ovate, densely aggregated into an ovate head (1 1/2' long), bractcate, about 5; perig. ovate, acuminate, compressed, bifid, scabrous on the margin, with a short, ovate, and scabro-cuspidate glume, which equals it: si 8 - 10' high. - Borders of fields and woods, common, but not abundant.

12 C. Muhlenbergii Schk. Spikelets alternate, obtuse, approximate into an orate-oblong head, 3/4 long, with a long bract at the lower one; perig. ovate, convex above, very smooth, nerved, bifid, scabrous on the margin, some diverging, a little shorter than the ovate and muronat glume; st. 12 - 18' high. - I* fields, not very common, readily distinguished from the three preceding and following.

13 C. stenophylla Wahl. Spikes 3 to 5, aggregated into a roundish head; perig. ovate, roundish-ventricous, subplano-convex, vained, scabrous or serrulate on the margin, bidentate, about equaling the ovate, acute glume; culm 3 to 6' high, smooth, with long, narrow leaves. - III. to Nebraska and Brit. Am.