Thorneochloa Romasch., P.M.Peterson & Soreng, gen. nov.

Peterson, Paul M., Romaschenko, Konstantin, Soreng, Robert J. & Reyna, Jesus Valdes, 2019, A key to the North American genera of Stipeae (Poaceae, Pooideae) with descriptions and taxonomic names for species of Eriocoma, Neotrinia, Oloptum, and five new genera: Barkworthia, x Eriosella, Pseudoeriocoma, Ptilagrostiella, and Thorneochloa, PhytoKeys 126, pp. 89-125 : 104

Thorneochloa Romasch., P.M.Peterson & Soreng, gen. nov.

Type.

Thorneochloa diegoensis (Swallen) Romasch. ≡ ( Stipa diegoensis Swallen).

Diagnosis.

Thorneochloa differs from Pseudoeriocoma Romasch., P.M. Peterson & Soreng in having dense pubescence 3-9 mm below the lower nodes, the hairs retrorse, non ramified branching on the middle and upper culms, and pedicels usually shorter than the spikelets.

Description.

Plants perennial, cespitose, not rhizomatous. Culms 70-140 cm tall, erect or ascending, often geniculate, 2-4 mm thick never bamboo-like or ramified above with (2) 3 nodes that are densely pubescent 3-9 mm below the lower nodes, the hairs retrorse, internodes usually pubescent. Leaf sheaths longer than the internodes below and shorter than the internodes above, glabrous or pubescent, ciliate on the margins and summit; collars with a tuft of hairs, the hairs 1.5-2 mm long; ligules 1-3 mm long, membranous and pubescent, apex truncate to obtuse; blades 15-40 cm long, 1-3.5 mm wide, flat to involute, scabrous below and pubescent above. Panicles 15-30 cm long, (2-) 4-8 cm wide, narrow, densely flowered, branches ascending appressed; pedicles usually shorter than the spikelets. Spikelets 8-11.5 mm long, lanceolate with one fertile floret without rachilla extension; disarticulation above the glumes; glumes 8-11.5 mm long, longer than the florets, subequal, hyaline, 3-5-veined, glabrous, acuminate; florets 5.5-7.5 mm long, usually fusiform; calluses 0.25-1.2 mm long, sharp, hairy; lemmas 5.5-7.5 mm long, fusiform, coriaceous, evenly hairy, the hairs 0.5-2 mm long, margins enveloping most of the palea, apex awned with minute apical lobes 0.2-0.4 mm long; lemma epidermal pattern maize-like; fundamental cells squared, longitudinally compressed with straight thin sidewalls subequal to silica cells (silica bodies) or shorter, regularly alternating; cork cells absent; lemmatal awns 20-50 mm long, 2-geniculate, flexuous, the segments scabrous, terminal segment straight; paleas 2.6-4 mm long, 1/2 to ¾ as long as the lemmas, 2-veined, veins not prolonged, hairy; anthers 2.5-4 mm long, not penicillate, 3 in number; lodicules 2 or 3; stigmas 2. Caryopses 3.8-4 mm long, fusiform, pericarp adherent, hilum linear, embryo ¼ the length.

Etymology.

The generic name honors Robert Folgers Thorne (1920-2015), an American taxonomist who specialized in the evolution and classification of vascular plants, known as the Thorne system.