[+] 1. Paucifloræ. Perigynium greenish, linear-lanceolate or almost needle shaped, not inflated, strongly deflexed at maturity, several times longer than the inconspicuous scale; spike androgynous, the pistillate flowers at base, few.—Sp. 1.
[+] 2. Lupulinæ. Perigynium green or greenish tawny or sometimes yellow, more or less inflated (except in n. 2–4) long, usually very turgid at base, mostly erect or nearly so, very gradually attenuate to a long slenderly toothed beak exceeding the scale; spikes 3 or more, the staminate mostly 1 and stalked, the pistillate often sessile, usually short and thick, often becoming dark colored in drying.—Sp. 2–8.
[+] 3. Vesicariæ. Perigynium smooth and shining, much inflated, at maturity straw-colored or sometimes purple, beaked and conspicuously short toothed (entire in n. 10), usually prominently few nerved, much shorter than in [+] 2; staminate spikes commonly 2 or more; pistillate spikes as a rule long and densely cylindrical.—Sp. 9–16.
[+] 4. Pseudocyperæ. Perigynium less inflated, more conspicuously nerved or even costate, and with more or less setaceous or awned teeth; scale usually awned; spikes mostly nodding or spreading, comose in appearance, greenish, greenish-yellow, or ochroleucous.—Sp. 17–19.
[+] 5. Squarrosæ. Perigynium obconic or obovoid, squarrose in exceedingly dense short spikes.—Sp. 20, 21.
[*] 2. Trachychlænæ. Perigynium mostly thick and hard in texture, often scabrous or hirsute, straight-beaked; pistillate spikes compactly flowered, mostly large, erect or nearly so; staminate spikes 1 or more; stigmas 3. Generally large and coarse.
[+] 1. Shortianæ. Terminal spike androgynous, staminate below; perigynium small, scabrous, nearly beakless, entire.—Sp. 22.
[+] 2. Anomalæ. Terminal spike all staminate; pistillate spikes long and cylindrical, mostly dense; perigynium broad and short, short-beaked, the orifice very slightly notched or entire, mostly granulate.—Sp. 23.
[+] 3. Hirtæ. A heterogeneous group, distinguished from [+] 2 by the longer and more deeply cut beak (slightly toothed in n. 24), and by the hairy perigynium (smooth in n. 25)—Sp. 24–27.
[+] 4. Paludosæ. Staminate spikes 2 or more, long stalked; the pistillate 2–several, usually all peduncled, long and heavy, loose-flowered, erect or nodding; perigynium large, thick in texture, strongly nerved, mostly smooth, usually conspicuously beaked. Coarse species.—Sp. 28, 29.