1 Style 5 (-6); capsule opening by 5 (-6) shallowly bifid valve

1 Style 3' capsule opening by 6 valve.

  2 Leaves narrow, usually linear, lanceolate, oblanceolate, or narrowly elliptic, the blade 3-10× as long as wide, 0.8-10 mm wide; stems prominently 4-angled.

    3 Sepal 2.0-3.5 mm long; petal 0-3.0 mm long, shorter than the sepal or absent; seeds 0.3-0.9 mm long.

      4 Inflorescence a leafy (or with obvious bract) terminal cyme of (1-) 5-50 flowers; seeds 0.7-0.9 mm long, smooth or slightly rugose.

        5 Bract subtending the pedicel green, herbaceous throughout; [Larbreae clade, Foliaceo-bracteatae subclade]

        5 Bract subtending the pedicel scarious (membranous), not foliaceous; [Larbreae clade, Parviflorae subclade]

      4 Inflorescence axillary, solitary or in small cyme of 2-5 flowers; seeds 0.3-0.8 mm long, distinctly papillose.

          6 Flowers in axillary inflorescence of 1-5 flowers; sepal 5; petal 5; seeds 0.3-0.4 mm long, with small, rounded tubercle; [widespread]; [Larbreae clade, Uliginosae subclade]

          6 Flowers solitary in leaf axil; sepal 4 (-5); petal absent; seeds 0.6-0.8 mm long, with stalked, knoblike tubercle; [of c. KY and TN]

    3 Sepal 3.5-9 mm long; petal 3.5-13 mm long, equaling or longer than the sepal; seeds 0.7-2.5 mm long.

             7 Seeds 2-2.5 mm long; bract of the inflorescence herbaceous; petal notched < halfway to the base

             7 Seeds 0.7-1.2 mm long; bract of the inflorescence scarious; petal notched > halfway to the base; [Larbreae clade].

               8 Sepal 4.5-5.5 (-7) mm long, strongly 3-nerved, narrowly lanceolate to triangular; leaves usually widest below the middle; seeds 0.8-1.2 mm long, coarsely tuberculate; inflorescence diffuse, many-flowered; [Gramineae subclade]

               8 Sepal (2-)3.5-4-5 mm long, weakly 3-nerved, ovate-elliptic; leaves usually widest at or above the middle; seeds 0.7-1.0 mm long, obscurely sculptured and appearing almost smooth; inflorescence more compact, fewer-flowered; [Parviflorae subclade]

  2 Leaves broad, usually ovate, obovate, or broadly elliptic, the blade 1-2.5× (or to 4×) as long as wide, 4-30 mm wide (if > 2.5× as long as wide, then definitely > 10 mm wide); stems terete or 4-angled.

                 9 Leaves long-petiolate, the petiole about as long as the blade, the blade cordate to truncate at the base; sepal 2.5-3.5 mm long, obtuse to broadly acute; seeds 0.6-0.8 mm long; stem glabrous or glandular-puberulent (the pubescence not in lines); [Petiolar clade]

                 9 Leaves sessile, short-petiolate, to long-petiolate (if long petiolate, the blade cuneate), the blade rounded to cuneate at the base; sepal 2.5-11 mm long, broadly acute to acuminate; seeds 0.4-2.0 mm long; stem puberulent to short-pilose (the pubescence in vertical lines or not).

                   10 Leaves (1.0-) 2.5-10 cm long (with strong dimorphism between sterile and fertile shoots, the leaves of sterile shoots much larger); seeds 1.7-2 mm long; sepal 4-11 mm long; stem pubescence in vertical lines or uniformly distributed; perennial, the stems strong and ascending to erect; [native]; [Insignes clade].

                     11 Sepal 3.5-7 mm long, acute, ciliate and more-or-less pubescent on the back; [widespread in our area]

                   10 Leaves 0.3-4.0 cm long; seeds 0.6-1.7 mm long; sepal 2.5-6.5 mm long; stem pubescence always in vertical lines; annual, the stems weak and in part prostrate, the tips or vigorous growth ascending; [exotic]; [Petiolar clade].

                       12 Sepal 5.0-6.5 mm long; stamen 8-10; seeds 1.1-1.7 mm long

                       12 Sepal 2.5-5.2 (-6.0) mm long; stamen 1-5 (-8); seeds 0.4-1.3 mm long.

                          13 Stamen 3-5 (-8); sepal 4.5-5.2 (-6.0) mm long, lacking red band at base; seeds 0.9-1.4 mm long; petal usually present

                          13 Stamen 0-3 (-5); sepal 3.0-4.0 mm long, frequently with a red band at the base; seeds 0.4-0.9 mm long; petal usually absent