| # Festuca of North America |

S.G. Aiken, M.J. Dallwitz, C.L. McJannet, and L.L. Consaul

### Festuca thurberi Vasey

THURBER'S FESCUE.

In Rothr. Cat. Pl. Geogr. and Geol. Explor. and Surv. W. 100th Meridian: 56. 1874. F. tolucensis subsp. thurberi St.-Yves, Candollea 2: 304. 1925. Type: U.S.A. Colorado: South Park, 1873, Wolfe 406 (Vasey 11154). Holotype: US! Isotype: GH!

Poa festucoides M.E. Jones, Proc. Calif. Acad. Sci. II. 5: 723. 1895, non Lam., Tabl. Encycl. 1: 182. 1791.

Poa kaibensis M.E. Jones, Erthea 4: 36. 1896. Type: U.S.A. Utah: Mt. Ellen, Henry Mountains, 25 July 1894, Jones 5671.

Habit. Plants deep green, 45–120 cm high, densely tufted (bunchgrass), tiller bases stiffly erect, bases not purplish (usually), horizontal rooting stems absent. Vegetative shoots arising from within existing sheaths.

Vegetative morphology. Sheaths glabrous or with trichomes (near the collar), conspicuous at the base of the plant, persisting for more than 1 year, remaining entire, not conspicuously splitting between the veins (striate), open more than half their length. Collars glabrous. Auricles absent (ligules decurrent). Ligules 2–5(–9) mm long, without cilia (scaberulous on the abaxial surface). Leaf blades 30–45 cm long, erect, stiffish. Adaxial blade surfaces with trichomes, abaxial blade surfaces with trichomes (usually harshly scabrous). Leaf blades plicate; 0.6–0.87–1.2 mm wide, 0.75–1.2–1.7 mm deep. Veins 9–15. Adaxial to abaxial sclerenchyma strands present. Abaxial sclerenchyma well developed, in broad bands or continuous (sclerenchyma varying in thickness). Ribs 9–13. Uppermost culm leaf sheaths not inflated. Flag leaf blades 5–15 cm long. Culm nodes becoming exposed, 1–2 (often purple); internodes glabrous (lower down), or scabrous-hirsute (near the inflorescence).

Floral morphology. Inflorescence (7–)10–15(–17) cm long. Inflorescence branches at the lowest node 1(–2), spreading (slightly drooping, commonly pulvinate), 4.5–9 cm long (the longest, half to two-thirds as long as the panicle). Rachis angular in cross section, trichomes over the entire surface. Spikelets aggregated towards the ends of the branches (that are often pulvinate at the base); 2–7 on the longest branches; (8–)10–14 mm long, 2.5–4 mm wide. Proliferating spikelets absent (not recorded for this taxon). Florets (3–)4–5(–6). Glumes unequal (sometimes approaching subequal), with trichomes (minute), vestiture over most of the outer surface, margins not ciliate. First glume 4–5 mm long, veins 1. Second glume shorter than the first lemma, 4.5–6.5(–7) mm long, veins 1–3. Rachilla internodes antrorsely scabrous (densely scaberulous). Lemma callus not elongated. Lemma (6–)6.5–8(–10) mm long, nerveless in dorsal view or sometimes with only the centre vein distinct, with trichomes (usually scaberulous), trichomes on the upper portion only (especially on the veins); apex entire. Lemma awn present (but very short) or absent. Lemma awn 0–0.2 mm long. Palea 6–7 mm long, distinctly pubescent between the keels. Lodicules with marginal teeth, glabrous, 1–1.2 mm long. Anthers 3–4.5 mm long. Ovary apex pubescent. Caryopsis 3.8–4.5 mm long.

Cytology. 2n = 28, or 42.

Habitat and distribution. Native. Oak brush woodlands in foothills to subalpine meadows. Southwestern USA: Ariz.; Rocky Mountains USA: Colo., Utah, Wyo.; South Central USA: N. Mex.

Classification. Subg. Leucopoa (Griseb.) Hack.

Notes. This species is named in honour of its discoverer, Dr. George Thurber (1821–90), botanist and quartermaster of the United States Mexican Boundary Commission (1850). Thurber was a professor of botany and horticulture at Michigan Agricultural College 1859–63 and editor of the American Agriculturalist 1863–90 (Dayton 1913).

Cronquist et al. (1977) noted that "Festuca thurberi is very closely related to F. campestris Rydb. (=F. scabrella Torrey in Hook.) and resembles it in all respects except for the prominent ligules and statistically shorter glumes and lemmas". Not only do the lengths of the ligules and the awns in the two taxa not overlap, but the ligules and glume margins in F. thurberi are glabrous and those in F. campestris are ciliate.

Illustrations. • Line Drawing. Illustration of F. thurberi from Piper (1906). • Leaf anatomy. Leaf cross section of F. thurberi. Leaf blades are 0.6–0.87–1.2 mm wide and 0.75–1.2–1.7 mm deep, with 9–15 veins. Adaxial to abaxial sclerenchyma strands are present. Abaxial sclerenchyma strands are well developed, in broad bands or continuous, sclerenchyma varying in thickness. There are 9–13 ribs. • Holotype specimen: US. Type specimen of F. thurberi from Colorado, South Park, 1873, John Wolf 11154. Holotype: US. • Isotype specimen: GH. Type specimen of F. thurberi from Colorado, South Park, 1873, John Wolf 11154. Isotype: GH. • Distribution map

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations with detailed captions, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa. See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Aiken, S.G., Dallwitz, M.J., McJannet, C.L. and Consaul, L.L. 1996 onwards. Festuca of North America: descriptions, illustrations, identification, and information retrieval. Version: 14th February 2019. delta-intkey.com’. Aiken, Dallwitz, McJannet, and Consaul (1997) should also be cited (see References).

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