Poa bigelovii Vasey & Scribn., Descr. Cat. Grass. U.S. 81. 1885.

Soreng, Robert J. & Peterson, Paul M., 2012, Revision of Poa L. (Poaceae, Pooideae, Poeae, Poinae) in Mexico: new records, re-evaluation of P. ruprechtii, and two new species, P. palmeri and P. wendtii, PhytoKeys 15, pp. 1-104 : 15-17

4. Poa bigelovii Vasey & Scribn., Descr. Cat. Grass. U.S. 81. 1885. Fig. 4 A-E

Poa annua var. stricta Vasey ex Scribn., Bull. Torrey Bot. Club 10(1): 31. 1883. Type: USA, Arizona, banks of the Rillita, 9 Apr 1881, C.G. Pringle s.n. (holotype: US-81668!; isotypes: NY-431203!, NY-431204!, US-723316!, US-824699!, US-914298!).

Poa bigelovii Vasey & Scribn., Contr. U.S. Natl. Herb. 1(8): 270. 1893 (isonym). Type: USA, New Mexico, 3 Jul 1847, A. Fendler 931 (holotype: US!; isotypes: MO-3048732!, MO-3048575!, NY-431217!,S-G-4935!).

Description.

Hermaphroditic. Annuals (rarely longer-lived); tufted, tufts sparse, small, bases narrow, green; tillers intravaginal (each subtended by a single elongated, 2-keeled, longitudinally split prophyll), without cataphyllous shoots, most shoots flowering. Culms (2-)5-60(-70) cm tall, erect or infrequently geniculate at base, slender, leafy, slightly compressed, smooth (or lightly scabrous above); nodes terete, 2-4, usually 1-2 exerted eventually. Leaf sheaths usually compressed and keeled, smooth or keels scabrous; butt sheaths papery, smooth, glabrous; flag leaf sheaths 2-10 cm long, margins fused 25-50% their length, 4 × longer to slightly shorter than its blade; throats and collars smooth, glabrous; ligules 2-6 mm long, usually decurrent, abaxially smooth or scabrous, apices obtuse to acute; blades of cauline leaves (1-)4-15 cm long blades 1-5(-6.5) mm wide, flat or folded, thin, soft, finely scabrous, broadly prow-tipped; flag leaf blade 1-7(-13) cm long, flag leaf blades 1-4(-8) cm long. Panicles (1-)5-15 cm long, mostly over 8 × longer than wide, erect, contracted, cylindrical, sometimes interrupted, congested to loosely congested; rachis with 2-3(-5) branches per node; primary branches erect or steeply ascending, more or less angled, sparsely to densely scabrous; lateral pedicels mostly less than 1/4 the spikelet in length, moderately scabrous, prickles moderately coarse; longest branches 1-7 cm, with 3-15(-25) spikelets in the distal 1/4-1/2. Spikelets 4-7 mm long, ovate to lanceolate, laterally compressed; not bulbiferous; florets 3-7, hermaphroditic; rachilla internodes terete, up to 1 mm long, smooth, glabrous; glumes narrowly lanceolate to lanceolate, subequal, distinctly keeled, keels and sometimes lateral veins scabrous, acute to acuminate; lower glumes 2.2-3.8 mm long, 1-3-veined; upper glumes 2.5-4.8 mm long, subequaling lowest lemma or slightly exceeding it, 3-viened; calluses dorsally webbed, web distinct, hairs woolly; lemmas 2.6-4.3 mm long, lanceolate, green to light green, sometimes slightly anthocyanic, distinctly keeled, smooth, keels to near the top, marginal veins to 2/3, and sometimes intermediate veins short to long villous, between veins glabrous or softly puberulent, intermediate veins obscure to moderately prominent, upper margins white to hyaline, apices acute, pointed or slightly blunt; paleas keels distally with a few hooks, medially softly puberulent to short villous over the keels, intercostal region usually softly puberulent. Flowers mainly cleistogamous; lodicules 0.45 mm long, lanceolate, with a slight lateral lobe at middle; anthers (1-2-)3, 0.2-1.0 mm long. Caryopses 1.8 mm long, narrowly elliptical in side-view, laterally compressed, light brown, sulcus narrow, hilum 0.3 mm long, elliptical, grain adherent to the palea. 2 n = 28, 28+I.

Distribution.

The species is endemic to the southwestern USA (Arizona, California, Colorado, Nevada, New Mexico, Oklahoma, Texas, and Utah) and northern Mexico. In Mexico it occurs in Baja California, Baja California Sur, Chihuahua, Coahuila, Nuevo León, and Sonora.

Ecology.

The species occurs in shady sites among rocks and shrubs, usually in loose soils in springtime-moist desert uplands to open slopes lower Pinus - Quercus forests. This species is associated with the Chihuahuan, Sonoran, and Mojave desert vegetation. It occurs between 420-2200 m, and possibly higher. Flowering January to May.

Specimens examined.

Mexico. Baja California: El Rancho Viejo, 30 Apr 1889, J.S.Brandegee 24 (US). hills behind Bahia de Los Angeles, 3700 ft [1130 m], 24 Feb 1963, R.S.Cowan 2344 (MEXU). Sierra Juárez, 32°27.5'N, 116°09.25'W, 1300 m, 8 May 1982, R.Moran 30600 (MEXU). Sierra La Libertad, Canyon La Borreguera, 9.5 miles E of Mission San Borja, 28°50'N, 113°40'W, 2400 ft [730 m], 27 Mar 1978, K.Nixon 1130, C.P.Cowan & M.L.Sauls (MEXU, TEX). Arroyo San Pedro near L a Bocana, 28°28'N, 113°25'W, 250 m, 11 Mar 1966, R.Moran 12512 (TAES). Baja California Sur: N slope of Cerro Azufre, 27°30'N, 112°36'W, 1650 m, 14 Apr 1973, R.Moran 20509 (MEXU, TAES); ditto, 17 Feb 1973, R.Moran 20173 & J.L.Reveal (TAES). Volcán las Tres Vírgenes, 1150 m, R.Moran 20411 (TAES, TEX, US). Chihuahua: ca. del Rio Chihuahua, 5 Apr 1886, G.G.Pringle (MEXU). Mountains. near Paso del Norte, G.R.Vasey s.n. (US). Canon de Tinaja de Corazon, east flank of Sierra de Mulato on Rio Grande 29°13'N, 103°45'W, 750 m, 13 Mar 1986, M.C.Johnston 12898 (TEX). canyon in north face of Sierra Rica, south of Rancho La Consolacion, 19°12'N, 104°05'W, 1400-2000 m, 3 May 1973, M.C.Johnston 10776 (LL). Coahuila: Saltillo, 9 Apr 1905, E.Palmer 532 (NY, US). ca. 2 km N of Estacion Carneros, E flank of Sierra El Chorreadero, 25°08'00"N, 101°07'20"W, 2150 m, 29 Mar 1973, M.C.Johnston 10498, T.L.Wendt & F.ChiangC. (MEXU, MO, TEX). Rio Grande, Tule Canyon above Upper Madison Falls, 29°44-45'N, 102°23'30"W, 475 m, 10 Apr 1973, M.C.Johnston 10618, T.L.Wendt & F.Chiang-C. (MEXU, TEX). Municipio Ramos Arizpe, Sierra de la Paila, 5 Jan 1966, Cano 15 (TAES). [Sierra de Santa Rosa], Rincón de María, on Hacienda La Babia, ca. 70 rd. mi. NW from Múzquiz, 28°27'30"N, 102°05'W, 1900 m, southwest part of rincón, southsouthwest of "Slump Spring", 27 Apr 1975, T.Wendt 901A & D.Riskind (LL). Sierra del Carmen, Rancho Moreros y Rancho San Isidro, ca 178 km de Múzquiz por la brecha Músquiz-Boquillas del Carmen (carretera 53), 28°47'N, 102°30'W, 1300 m, 27 Mar 1992, M.A. Carranzal 398, J.Noriega & L. García (TEX). Nuevo León: Monterey, 17-26 Feb 1880, E.Palmer 1365 (US). Sierra Madre above Monterey, 3000 ft [misprint for 8000 ft? = 2440 m], 31 Mar 1906, C.G.Pringle 13748 (MO, TEX, US). Sonora: N end of Sierra El Viejo, in the large canyon containing Mina Santa Cruz, 25 miles SW of Caborca, vic. 30°22'N, 112°22'W, 1700 ft [520 m], 7 Mar 1983, A.C.Sanders 3527, M.Dimmitt & G.Montgomery et al. (MEXU). SW of Sonoyta on Mexico Highway 8, 31°50'N, 112°56'W, 420 m, 30 Mar 1988, R.S.Felger 88-151 & A.D.Zimmerman (MEXU). Municipio Yecora, 3.5 km W of Santa Ana road, 4.8 km E of San Nicolas road, on Mexico 16, 28°25'40"N, 109°08'50" W, 720 m, 31 Mar 1997, A.L.Reina-G. 97-466 & T.R.VanDevender (MEXU, TEX). 1.5 km SW of Santa Ana on road to Guadalupe Tayopa, 28°22'54"N, 109°09'30"W, 775 m, 21 Feb 1997, T.R.VanDevender 97-207 & A.L.Reina-G. (MEXU, TEX).

Discussion.

Presumably because of its early spring flowering and dependence on winter and early spring precipitation, this species is infrequently collected in Mexico.Its annual habit and narrow, congested panicles, combined with a web on the callus of the lemma, distinguish it from all other species of Poa . The Cano 15 specimen from Coahuila is unusual because the panicle is open and the branches are naked in the lower half, but otherwise it aligns near Poa bigelovii . It was originally determined as " Poa chapmaniana Scribn.?" (but it has 3 anthers ca. 1 mm long, versus 1 ca. 0.2 mm long), then as Poa annua (by Gould in 1966), but it is quite scabrous on the branches and has a strong web on the callus like Poa bigelovii . Plants from Municipio Ramos Arizpe should be examined more closely as a possible new species.

Figures

Figure 4. A-E Poa bigelovii Vasey & Scribn. A habit B blade apex abaxial view C inflorescence D spikelet E lemma and palea F-M Poa occidentalis (Vasey) Vasey F habit G sheath, collar, blade, abaxial view H sheath, ligule, blade I inflorescence J branch segment with spikelets K spikelet L floret M palea. Drawings from Soreng (2007).