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Key to Tridens

Poaceae

Tridens

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(c) Sorrie, Bruce A. - CC-BY
1 Panicle dense and spike-like, > 4× as long as wide, the branches ascending to appressed.
  2 Spikelets 4-6 mm long; glumes always conspicuously longer than the adjacent lemmas (usually ca. 2x as long and exceeding the distal florets); lemmas 2.5-3.0 mm long
  2 Spikelets 5-10 (-13) mm long; glumes ca. as long as the adjacent lemmas (never conspicuously 2x as long and not or only scarsely exceeding the distal florets); lemmas 3-5 (-10) mm long
    3 Plants rhizomatous, with elongated and thickened rhizomes; each of the 3 lemma veins excurrent; calluses pilose
    3 Plants cespitose, with shortly rhizomatous bases (often hardened and knotty but never elongated); lemma veins either not excurrent or only the midveins shortly excurrent; calluses glabrous or shortly pilose.
      4 Paleas not widened nor bowed-out below; caryopses dorsally flattened and deeply concave to folded on the dorsal (hilar) surface
        5 Upper glume 3-7-veined, 5.5-10 mm long; leaves mostly 3-4 mm wide; culms 4-8 cm tall
        5 Upper glume 1-veined, 4-5 (-6) mm long; leaves 1-2 mm wide; culms < 5 (-6) dm tall
      4 Pales widened or bowed-out below; caryopses not dorsally flattened nor deepy concave on the dorsal surface.
          6 Panicles 8-25 cm long; lateral veins of the lemmas glabrous or only basally pubescent, the midveins ending before the distal margin (not excurrent); [KS south through TX, waif e. of MS river]
          6 Panicles 5-8 (-10) cm long; lateral veins of the lemmas pilose, the midveins shortly excurrent; [TX only]
(c) Ware, Richard & Teresa - CC-BY-NC, permission granted to NCBG
1 Panicle open and spreading, < 4× as long as wide, the branches well-developed and spreading-ascending to reflexed. Add T. texanus
             7 Lateral veins of the lemmas not excurrent (rarely reaching the distal margin of the lemmas); lower glumes either 2.0-2.5 mm long (Triplasiella) or if 4-6 mm long (as in Tridentopsis buckleyana) then not mucronate.
               8 Lower glumes 4-6 mm long; ligules 0.4-1.0 mm long; spikelets 7-10 mm, with 2-5 florets
               8 Lower glumes 2.0-2.5 mm long; ligules 1.2-3.0 mm long; spikelets 3-7 mm long, with 5-12 florets
             7 Lateral veins of the lemmas excurrent; lower glumes 4.0-4.5 mm long (if 2.5-3.0 mm long as in T. flavus and T. chapmanii, then the tips also usually mucronate).
                 9 Spikelets 4-5 mm long, 2.5-3.5 mm wide; all pedicels shorter than 1 mm long
                 9 Spikelets 6-13 mm long, 1.5-2.2 mm wide; pedicels > 1 mm long.
                   10 Leaf blades 1-5 mm wide; culms 20-75 cm tall; panicles 5-16 cm long; spikelets 6-13 mm long, each with 6-12 florets; [TX]
                   10 Leaf blades 3-10 mm wide; culms 60-80 cm tall; panicles 14-40 cm long; spikelets 5-10 mm long, each with 4-8 florets; [collectively widespread, including TX]
(c) Fleming, Gary P.
                     11 Primary pulvini densely pubescent, the hairs encircling the base of the panicle branch; secondary pulvini pubescent; spikelets mostly on pedicels 3-20 mm long, these divergent from the inflorescence branchlets; main branches of the inflorescence stiffly spreading
(c) Ware, Richard & Teresa - CC-BY-NC, permission granted to NCBG
                     11 Primary pulvini glabrous to sparsely pubescent, tufted only in the axil (the upper surface of the panicle branch); secondary pulvini glabrous; spikelets on pedicels mostly < 3 mm long, these mainly appressed to the inflorescence branchlets; main branches of the inflorescence spreading, ascending or drooping