Psorothamnus scoparius

Title

Psorothamnus scoparius

Authors

Rupert C. Barneby

Scientific Name

Psorothamnus scoparius (A.Gray) Rydb.

Description

7.  Psorothamnus scoparius (Gray) Rydberg

(Plate V)

Sparsely leafy, in late summer almost leafless broomlike shrubs or subshrubs up to 1 m tall, with many pliantly erect and incurved-ascending, freely forking stems densely gray-strigulose with short, appressed or subappressed, retrorse, partly scalelike hairs and thickly charged with small orange blister-glands, the sparse deciduous foliage greenish-gray, more thinly stigulose than the stems with antrorsely subappressed hairs, the inflorescence gray-pilosulous; leaf-spurs 0.2-1 mm long; stipules subulate, 0.3-0.7 mm long, livid-glandular and glabrous at tip, deciduous; post-petiolular glands 0, or in 3-foliolate leaves small and prominent; leaves (2) 4-20 mm long, mostly simple, composed of a short petiolule and a terminal, linear-oblanceolate, retuse, thick-textured, folded leaflet prominently tuberculate beneath, a few (but not on all plants) developing a petiole+rachis up to 5 mm long bearing at apex a terminal and 2 much smaller but otherwise similar leaflets; peduncles terminal to all ultimate branchlets, 0.5-9 cm long; racemes short but not dense, mostly ± 5-15-flowered, ovate in outline, without petals (7) 8-10 mm diam, the hirsutulous axis becoming (1) 3-18 mm long, sometimes a few flowers scattered below the main spike; bracts early deciduous, papery, ovate- or oblanceolate-acuminulate, gland-tipped, pilosulous dorsally, 1.5-2.5 mm long; pedicels thick, 0-0.4 (0.7) mm long, densely pilosulous, charged with a pair of orange glands distally; calyx 3.5-4.5 mm long, densely gray-pilosulous, subspathaceous, the tube (measured to a dorsal sinus) 2.2-3 mm long, the ribs moderately prominent, the sub- membranous intervals charged with 1 row of (1) 2-5 orange glands, the ovate teeth unequal, the ventral pair longest and broadest, united to within 1 mm of tips but (1) 1.3-2 mm long measured from a lateral sinus, the dorsal tooth shortest and narrowest, all charged at tip and on each lateral margin with a blunt gland; petals (deciduous) vivid blue or blue-violet (exceptionally white), all or all but keel charged with apical glands; banner 6.4-9 mm long, the forwardly arched claw 2-2.7 mm, the oblong- obovate, basally cordate, apically notched blade 5-6.6 mm long, 3.6-4.2 mm wide; wings 7.1-9.1 mm long, the claw 2.1-2.8 mm, the narrowly oblong-oblanceolate, obliquely notched blade 5-6.7 mm long, 1.7-2.1 mm wide; keel 6.1-8.3 mm long, the claws 1.8-2.9 mm, the obliquely obovate, glabrous or thinly puberulent blades (4.2) 4.6-5.8 mm long, 2.1-3.5 mm wide; androecium 10-merous, 5.5-8.5 mm long, the longer filaments free for 2.3-2.6 mm, the connective gland-tipped, the anthers 0.6-0.85 mm long; pod slightly exserted, ± 4 mm long, glabrous at base, pilosulous and gross-glandular distally; seed castaneous, sometimes purple-speckled, 2.1 -2.7 mm long; n = 10 (Spellenberg, 1973). — Collections: 44 (vi).

Dunes and sandy river-beds, locally abundant, 1100-1530 m (± 3670-5100 ft), very common along the Rio Grande from near Albuquerque, Bernalillo County, New Mexico downstream to El Paso and immediately adjoining Hudspeth counties, Texas, in New Mexico interruptedly e. to the White Sands in Otero County, and w. to Luna County and (isolated) the Wilcox playa in Cochise County, Arizona, s. to the great dunes of n. Chihuahua in mpos. C. Juarez and Villa Ahumada; apparently disjunct around margins of Bolson de Mapimi in w.-centr. Coahuila (Mohovano; Sa. del Rey) and immediately adjoining s.-e. Chihuahua. — Flowering June to October. —Representative: UNITED STATES. Arizona. Cochise: Shreve 4256 (UC). New Mexico. Bernalillo: Jones 4135 (BR, NY, POM, UC); Heller 15,796 (NY, UC). Valencia: Barneby 13,840 (CAS, DS, GH, NY, US). Socorro: McVaugh 3907 (UC); Barneby 13,846 (NY). Dona Ana: Wooton 9 (NY, UC); Barneby 13,850 (CAS, NY). Otero: Cutler 2017 (UC). Luna: Shreve 8226 (UC). Texas. El Paso: Waterfall 3904 (NY); Warnock 5761 (OKLA, RENNER). Hudspeth: Wamock 13,766 (RENNER, TEX). MEXICO. Chihuahua. Ciudad Juarez: Pringle 719 (BR, F, M, MEXU, NY, UC, W). Villa Ahumada: Gentry 8213 (MEXU, UC); Ripley & Barneby 13,854 (CAS, NY). Jimenez: Mueller 3320 (UC). Coahuila. Sierra Mojada: Purpus 4491 (F, UC).

Psorothamnus scoparius (Gray) Rydb., N. Amer. Fl. 24: 48. 1919, based on Dalea scoparia (broomlike) Gray, Mem. Amer. Acad. II, 4 (Pl. Fendl.): 32. 1849. — "Jornada del Muerto, between Santa Fe and El Paso del Norte, Dr. Wizlizenus" — Holotypus, Wislizenus 86, GH! — Parosela scoparis (Gray) A. Hell., Catal. N. Amer. Pl., ed. 2, 7. 1900.