Tridens congestus (L. H. Dowey) Nash, pink tridens. Perennial herb, rhizomatous, fibrous–rooted, not rosetted, cespitose (bunchgrass), many–stemmed at base, ascending, in range 40—75 cm tall; shoots with several basal leaves and cauline leaves, glabrous; rhizomes with crowded nodes, of mature subunit of bunchgrass commonly wedge–shaped, 10 × 5 × 3.5 mm, whitish but brownish at nodes, internodes < 1—2 mm long; adventitious roots nodal, tough.
Stems (culms) cylindric, to 2.5 mm diameter, exposed, often bent at nodes, (geniculate), older nodes often dark red–purple; internodes hollow.
Leaves alternate distichous, simple with sheath; sheath open and > 360° so overlapped margins at node, with many fine ridges, margins membranous only near node and above minutely toothed along both margins, without lobes (auricles) at top; ligule membranous–ciliate, in range ca. 0.5 mm long; blade linear and often strongly inrolled as cylinder, to 285 × 1.5—5.5 mm, the widest near base, minutely toothed on margins base–to–tip, parallel–veined with veins raised on both surfaces and midrib not present, upper surface (inrolled) often bluish green and minutely scabrous along veins, lower (outer) surface green totally without hairs and teeth.
Inflorescence spikelets, in terminal panicles, panicle ± condensed, 55—90 × 1.5—2.5 mm, with 1—2 principal branches per node, branches ascending and having 1—4 branchlets each with to 4 spikelets, spikelets 150+, each spikelet with (4—)5—10(—12) florets, bracteate, not awned; peduncle cylindric (never angular), to 280 mm long, the basal portion within sheath of flag leaf, glabrous; rachis somewhat fine–ridged and angled, to 80 mm long, flexuous, somewhat striped, glabrous; bract subtending the lowest branch acuminate, to 5 mm long, often purple, bract subtending other branches absent; branches to 20 mm long; stalk of spikelet short—1.5 mm long, glabrous.
Spikelet slightly compressed–ovoid, 6.5—8 × 3—3.5 × 1.5 mm (including vein extensions, mucrons), with pilose hairs visible on lemmas, breaking above glumes and between florets and persistent; rachilla conspicuous at anthesis appearing zigzagged, segments cylindric, straw–colored; glumes 2, subequal, boatlike, lower glume cupped–ovate, ca. 2.9 × 2 mm, upper glume cupped–obovate, ca. 3.2 × 2.2 mm, 1–veined, acute at tip, keeled, the keel glossy green and glabrous but minutely scabrous with several teeth approaching tip, with wide membranous margins often pinkish base–to–tip or above midpoint, with microhairs on outer surface near tip; callus with short hairs; lemma with short extension of midvein, body cupped–obovate, in range (1.7—)3—4.2 × to 2.4 mm, 3–veined, membranous and above midpoint often pink to rose, notched at tip, veins raised and not converging at tip, veins green above midpoint and densely pilose–ciliate below green but in range not ciliate to base, the hairs conspicuous and visible on faces of spikelet, the extension of central vein 0.3—0.5 mm long, pink to rose, minutely barbed, the lateral veins parallel and mostly not reaching margin, if reaching margin vein rarely with a short extension, if not reaching margin sometimes approaching a membranous tooth, margins from lateral vein to tip minutely fringed, notch to 0.2 mm deep and with acute lobes, outer surface with microhairs near tip; palea in outline inverted heart–shaped cupped and flexed away from lemma, slightly shorter than lemma and blunt at tip, 2–veined, 2–keeled strongly folded along veins enclosing ovary, opaque whitish with green keels, folded margin 0.5—0.65 mm wide, below midpoint the “lobes” clearly visible on side of each floret projecting from lemma, above exposed lobes minutely scabrous along keels.
Flower bisexual (terminal florets sterile or immature); perianth (lodicules) 2, often eaten by small insects; stamens 3, free, exserted; filaments threadlike, to 3 mm long, colorless; anthers basifixed, dithecal, ca. 1.2 mm long, reddish–purple fading after dehisced, longitudinally dehiscent; pollen white; pistil 1; ovary superior, somewhat wedge–shaped truncate at top, ca. 0.7 mm long, pinkish, 1–chambered with 1 ovule; styles 2, widely spaced at top of ovary and widely spreading, exserted below midpoint of lemma, ca. 1.5 mm long, colorless at base, above midpoint red–purple with long stigmatic hairs.
Fruit achene (caryopsis), dispersed as a floret tightly enclosed within adherent palea and lemma + a rachilla segment; achene ellipsoid somewhat flattened front–to–back, ca. 1.6 × 0.8 mm, initially pale green with purple at truncate top aging brown, before drying with widely spreading, widely space styles (lower portion).
A. C. Gibson