泰国苞茅 tai guo bao mao

Hyparrhenia rufa (Nees) Stapf var. siamensis Clayton.

Perennial. Culms erect, slender to robust, 1–3 m tall. Leaf sheaths glabrous; leaf blades 30–60 × 0.2–0.8 cm, glabrous, margins scabrid; ligule subrounded, ca. 2 mm. Spathate panicle variable, lax or contracted; spatheoles linear-lanceolate, 3–5 × 0.3–0.5 cm, finally reddish and rolled; peduncle shorter or longer than spatheole, usually flexuously exserted at least on panicle periphery, glabrous or white bearded. Racemes 6–7-awned per pair, rufous, not reflexed at maturity; raceme bases unequal, terete, glabrous, upper 3–5 mm; 1 pair of homogamous spikelets at base of lower raceme, 1–2 pairs at base of upper raceme. Sessile spikelet 4–5 mm; callus narrowly cuneate, 1–1.2 mm, densely white or golden bearded; lower glume oblong-lanceolate, brownish, glossy, typically with scanty stiff rufous hairs, but sometimes glabrous or pubescent; awn 2–3 cm, the column pubescent with stiff brown hairs. Pedicelled spikelet 3–5 mm, acute.

Hill slopes; 800–1200 m. Yunnan [Myanmar, Thailand].

This taxon is a uniform, local segregate from the gene pool of the extremely variable, African species Hyparrhenia rufa (Nees) Stapf. Hy-parrhenia rufa s.s. has been introduced to warm parts of America and elsewhere as a pasture grass and is recorded from Yunnan. It has 7–14 awns per raceme pair, a shorter (0.2–0.8 mm) callus, and a slightly shorter sessile spikelet.

Hyparrhenia yunnanensis can be distinguished from the other species in China (except H. griffithii) by its long, slender upper raceme base, which may sometimes be partially connate with the shorter lower raceme base. The brown color of the spikelet hairs is also distinctive, although it may sometimes be rather pale.