Keys prepared by Richard W. PohlÜ and Kenton L. Chambers for the Manual of Grasses for North America

A key for grasses with variously concealed, spiny, or highly modified spikelets.

1 Bisexual or pistillate spikelets 1 to many, almost wholly concealed within the upper sheaths (staminate inflorescences exserted in BuchloŽ) (2)
1 Bisexual or pistillate spikelets usually many, borne on exserted inflorescences (7)

2(1a) All spikelets unisexual; pistillate spikelets falling 3-5 together as a bur-like cluster, the florets concealed by enlarged, rigid, 3-lobed glumes; staminate spikelets exserted, borne on spike-like branches; most plants unisexual  BuchloŽ
2 Some or all spikelets bisexual or, if unisexual, the pistillate spikelets not falling as a bur-like cluster (3)

3(2b) Plants annual, often much-branched and mat-forming (4)
3 Plants perennial, stoloniferous or rhizomatous (5)

4 Spikelets with 1 floret, disarticulating above or below the glumes; lemmas glabrous Crypsis
4 Spikelets with 3-4-florets, disarticulating above the glumes and between the florets; lemmas with tufts of hair on the margins  Munroa

5 Spikelets subtended by bristles; florets bisexual; introduced lawn grasses, often escaping and weedy Pennisetum  
5 Spikelets not subtended by bristles; some or all florets unisexual (6)

6(5b) Plants unisexual; spikelets not in triplets, lacking glumes; pistillate spikelets with 2-5 florets; native coastal species of the Gulf of Mexico and California  MonanthochloŽ
6 Plants bisexual; spikelets in triplets of 1 sessile spikelet and 2 pedicellate ones, the triplet enclosed in a boat-shaped sheath; all spikelets with 2 glumes and 2 florets; central spikelet sessile and bisexual; lateral spikelets pedicellate and staminate or sterile; rare, introduced species  Apluda

7 Inflorescence bristly, the spikelets concealed by straight or hooked spines or bristles (8)
7 Inflorescence not bristly (10)

8 Spikelet clusters covered with spines arising from enlarged glumes, the spines usually hooked 31.50 Tragus  
8 Spikelet clusters covered with spines or bristles, but these not arising from the glumes and usually straight (9)

9(8b) Spikelets hidden inside retrorsely barbed spiny burs  Cenchrus
9 Spikelets more or less hidden by a tuft of smooth, plumose, or antrorsely barbed bristles Pennisetum

10(7b) Inflorescence spike-like, bearing detachable fascicles of spikelets; rachis zig-zag Anthephora
10 Inflorescence usually not spike-like, never bearing detachable fascicles of spikelets (11)

11(10b) Plants stoloniferous or rhizomatous; culms 10-30 cm tall; inflorescence a solitary club-shaped spike that breaks transversely; spikelets bisexual, more or less embedded in 2 or 4 rows on 1 side of the corky rachis; cultivated for turf and  lawns, frequently escaping  Stenotaphrum
11 Plants cespitose or rhizomatous, without stolons; culms 100-300 cm tall; spikelets unisexual, not embedded on either side of a corky rachis (12)

12(11b) Pistillate spikelets 3, concealed by bony, spherical beads (modified leaf sheaths), only the stigmas and a short branch of staminate spikelets protruding from each bead Coix  
12 Pistillate spikelets several to many, borne in a bony segmented spike, or concealed within sheaths on a cob (13)

13 Staminate spikelets in a terminal panicle (the tassel); pistillate spikelets in axillary spikes (cobs) concealed by leafy sheaths; cultivated for food Zea  
13 Staminate and pistillate spikelets borne together in terminal spikes, the pistillate spikelets embedded in a bony, cylindrical rachis with 1 glume exposed; rachis flattened distally, bearing numerous pairs of staminate spikelets; native species Tripsacum

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