GrassBase - The Online World Grass Flora


W.D. Clayton, M. Vorontsova, K.T. Harman & H. Williamson

© Copyright The Board of Trustees, Royal Botanic Gardens, Kew.

Poa tracyi

HABIT Perennial; caespitose. Butt sheaths herbaceous. Culms geniculately ascending, or decumbent; 25–125 cm long. Culm-internodes terete. Leaves cauline. Leaf-sheaths tubular for much of their length; with 0.5–0.9 of their length closed; keeled; puberulous. Ligule an eciliate membrane; 2–4.5 mm long; glabrous on abaxial surface, or pubescent on abaxial surface; obtuse, or acute. Leaf-blades 6–18 cm long; 2–5.5 mm wide; glaucous. Leaf-blade midrib keeled beneath. Leaf-blade surface glabrous. Leaf-blade apex hooded.

INFLORESCENCE Bisexual, or gynodioecious ("male", in this context, indicating the bisexual state); with male and female spikelets in the same inflorescence, or with male and female spikelets in different inflorescences. Inflorescence a panicle.

Panicle open; pyramidal; 13–29 cm long. Primary panicle branches spreading, or reflexed; 1–5 -nate; 2.5–8 cm long. Panicle branches scabrous.

Spikelets solitary. Fertile spikelets pedicelled.

FERTILE SPIKELETS Spikelets comprising 2–8 fertile florets; with diminished florets at the apex. Spikelets lanceolate, or oblong; laterally compressed; 3–8 mm long; breaking up at maturity; disarticulating below each fertile floret. Rhachilla internodes eventually visible between lemmas; smooth. Floret callus woolly.

GLUMES Glumes persistent; similar; shorter than spikelet. Lower glume oblong; 0.5 length of upper glume; membranous; 1-keeled; 1 -veined. Lower glume lateral veins absent. Lower glume apex acute. Upper glume lanceolate; 0.9 length of adjacent fertile lemma; membranous; 1-keeled; 1–3 -veined. Upper glume lateral veins absent, or obscure. Upper glume apex acute.

FLORETS Fertile florets bisexual, or female. Fertile lemma lanceolate; lanceolate in profile; 2.6–5 mm long; membranous; much thinner on margins; keeled; 5 -veined. Lemma midvein ciliate; hairy below. Lemma lateral veins with distinct primaries but obscure intermediates. Lemma surface puberulous; hairy at base. Lemma margins ciliate; hairy below. Lemma apex obtuse. Palea 0.9 length of lemma. Palea keels scaberulous. Palea surface glabrous, or pubescent; hairy below. Apical sterile florets resembling fertile though underdeveloped.

FLOWER Lodicules 2; membranous. Anthers 3; 1.25–3 mm long.

FRUIT Caryopsis with adherent pericarp. Hilum punctiform.

MALE Male inflorescence bisexual similar to female. Male spikelets resembling female.

DISTRIBUTION North America: south-central USA.

NOTES Poeae. Soreng 1992.

Please cite this publication as detailed in How to Cite Version: 3rd February 2016.