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CPIE Notebook Project - Common Hawaiian Grasses Page 18

Key to Genus Dichanthium Willemet

Grasses of the genus, Dichanthium are medium size, clumping grasses that are relatively distinctive in the field with subdigitate racemes and long awns. These grassses are not commonly encountered, although can be abundant where they occur. Racemes typically (1)2 to 6 (or more) in number, sometimes appearing paired. Spikelets are paired, one sessile with an awn and one pedicellate without an awn. Superficially these grasses resemble the very common pitted beardgrass (Bothriochloa), although the raceme is slightly more robust. Four species are recorded from the Hawaiian Islands (Clayton & Snow, 2010; Imada, 2012); all are introduceed species.

Perennial, tufted, medium size; ligule membranous; leaves narrow, may be aromatic.

106a (104) Inflorescence of one to 1 to 3(6) racemes, these typically paired on erect branchlets with dense hairs (pubescent) ringing the branchlet below each raceme and extending a ways down the common branch or culm. A distinct, short column of dense white hairs occurs at each exposed culm joint. { Naturalized in lawns, pastures, and disturbed sites. Wilder grass. [NAT]
Dichanthium aristatum (Poir.) Hubb.

106b Branchlet below single or paired racemes hairless (glabrous) [107]
107a (106) Magnifying Lens Inflorescence of one to 2 to 5 racemes. Lower glume of sessile spikelet conspicuous (purple if fresh) with long (ciliate) hairs on border thinning from base. Australian bluestem. [NAT]
Dichanthium sericeum (R. Br.) A. Camus

107b Lower glume of sessile spikelet without long (ciliate) hairs on border, glabrous or with short hairs only. [108]
108a (107) Magnifying Lens Inflorescence of one to (1)2 to 15 racemes. Lower glume of sessile spikelet narrow oblong, with sparse hairs along margin above the middle. Angleton grass. [NAT]
Dichanthium annulatum (Forssk.) Stapf

Lower glume of sessile spikelet elliptic to obovate, glabrous or nearly so. Racemes attached at a common point (digitate). [NAT]

Dichanthium tenue (R. Br.) A, Camus

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