Barkworthia 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 : 92

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

Type.

Barkworthia stillmanii (Bol.) Romasch., P.M. Peterson & Soreng (≡ Stipa stillmanii Bol.).

Diagnosis.

Barkworthia differs from Piptatherum P. Beauv. in having spikelets with a pilose callus, paleas with prolonged veins, and 2-lobed lemma apices with lobes 1-3 mm long; and differs from Achnatherum in having saw-like lemma epidermal pattern, not the maize-like pattern characteristic of all achnatheroid grasses.

Description.

Plants short-rhizomatous perennials. Culms 60-150 cm tall with 2-5 puberulent nodes, 2-5 mm thick below, often geniculate. Leaf sheaths mostly glabrous or distally ciliate; collars glabrous or pubescent; ligules 0.2-0.5 mm long, membranous, apex truncate; blades 15-30 cm long; 3-7 mm wide, scabrous. Panicles 10-24 cm long, 1.5-3 cm wide, contracted; branches appressed, ascending, lower branches 2-3.5 cm long. Spikelets 14-18 mm long, lanceolate, subterete with one fertile floret without rachilla extension, disarticulation above the glumes; glumes 14-18 mm long, single-awned, the awns 2-3 mm long; lower glumes 1-3-veined, upper glumes 3-5-veined; florets 8-10 mm long, fusiform; calluses 0.5-1.2 mm long, rounded, pilose; lemmas 3-veined, evenly hairy, the hairs about 1.5 mm long, apex 2-lobed, the lobes 1-3 mm long with awnlike tips, narrow; lemma epidermal pattern saw-like; fundamental cells of variable length with sinuous sidewalls 2-7 times longer than silica cells irregularly alternating; silica bodies elongated-rectangular with straight or very shallow contracted sidewalls; cork cells not prominent; lemmatal awns 18-30 mm long, terminal, awned from the sinus, scabrous, 1 or 2-geniculate, persistent; paleas as long or longer than lemmas, 2-veined, hairy, the veins 1-3 mm prolonged reaching almost to the tip of the lemma lobes; anthers 4-6 mm long, penicillate, 3 in number; lodicules 3; stigmas 2. Caryopses fusiform, pericarp adherent, hilum linear.

Etymology.

The generic name honors Mary Elizabeth Barkworth, a well-known American agrostologist, who has contributed many papers investigating the taxonomy of the Stipeae .