154.  Dalea parrasana Brandegee

(Plate CXXXVIII)

Low suffruticose perennial herbs with woody roots (yellow beneath the brown bark) and shortly forking caudex, strigose-pilosulous with straight, subappressed and often a few narrowly ascending hairs up to 0.4-1 mm long, the several or numerous, eglandular, commonly canescent stems erect and ascending in low tufts, mostly simple, rarely 1-3-branched distally, the spikes solitary, terminal, the foliage gray, the leaflets pubescent both sides, minutely dotted beneath; leaf-spurs 0.5-1 mm long; stipules narrowly subulate to linear-caudate, 1.5-4.5 mm long, early becoming dry, stiff, fragile, stramineous below the livid tips; leaves petioled, 1-3 (3.5) cm long, all (or all but a few uppermost) 5 (7)-foliolate, the margined, punctate petiole 2-8 (13) mm, the rachis 1-9 (14) mm long, the leaflets narrowly ovate to lanceolate or rhombic- elliptic, acute to short-acuminate, flat or loosely folded, 3-15 mm long, all carinate dorsally by the midrib, the terminal one longest, stalked; spikes sessile or nearly so, ovoid, moderately dense, without petals 1.5-2.2 cm diam, the axis becoming 0.5-3 (3.5) cm long; bracts persistent through anthesis, subhomomorphic (the lowest a little smaller and firmer), broadly oblong- or ovate-elliptic, short-acuminate, 6-12 mm long, 3.4 -4 mm wide, navicular and embracing (almost concealing) the calyx, pallid at base, submembranous, green or purplish distally, delicately reticulate-nerved, dorsally thinly pilose or subglabrous, minutely punctate, ciliate; calyx 7.2-11.8 mm long, thinly pilose with fine spreading lustrous spiral hairs up to 2-3.5 mm long, the broadly campanulate tube 2.2-3.4 mm long, recessed behind banner, the ribs slender, scarcely prominulous, the flat membranous intervals charged with 1 row of 3-4 small transparent glands, the deltate-aristate, plumose, livid-tipped teeth 4.5-8.4 mm long; petals yellow fading brown or pinkish-brown, eglandular, the epistemonous ones perched below middle of androecium; banner 4.5-6.3 mm long, the claw 2.2-3 mm, the deltate-cordate blade 2.5-3.8 mm long, 2.8-4 mm wide; wings 5-5.4 mm long, the claw 1.2-2 mm, the obliquely obovate-elliptic blades 3.8-4.7 mm long, 2-3 mm wide; keel 5.5-6.5 mm long, the claws 1.7-2.5 mm, the almost half-obovate blades strongly oblique, 4.3-5.9 mm long, 2.3-3.5 mm wide; androecium 10-merous, 7.5-9 mm long, the longer filaments free for 2.6-3 mm, the greenish-yellow anthers (0.7) 0.8-1.4 mm long; ovary pilosulous distally, the pod and seed not seen. — Collections: 6 (i).

Dry rocky or shaley hills, commonly on or near gypsum outcrops, 1525-1800 m (5080-6000 ft), local, known only from s. Coahuila (mpos Parras, Saltillo, Ramos Arizpe) and from an unspecified station in San Luis Potosi.—Flowering August - November, perhaps also in spring. —Material: Coahuila. Parras: Parras, Purpus in 1905 (UC); Henrickson 6160 (TEX). Saltillo: 10 mi w. of Saltillo, Ripley & Barneby 13,282 (CAS, K, MEXU, MICH, NY, US). Ramos Arizpe: 12 km n. of Saltillo, Ripley 14,971 (NY). San Luis Potosi:—, Parry & Palmer 162 (NY).

Dalea parrasana (of Parras, Coahuila) T. Bdg., Univ. Calif. Pub. Bot. 4: 179. 1911.— "No. 4741, collected on Sierra de Parras, Coahuila..." Holotypus, collected by C. A. Purpus in oct 1910, UC! isotypus, US!

This sharply distinct species was collected first, somewhere in San Luis Potosi, by Parry & Palmer and misidentified as A. wrightii, which its dwarf stature and 5-foliolate leaves superficially suggest. The specimens were later mentioned by Vail (Bull. Torrey Club 24: 16. 1897) as representing a small form of Parosela wrightii intergradient to P. luisana. The latter resembles D. parrasana in its appressed vesture but differs greatly in its trifolio- late cauline leaves, smaller bracts, and much smaller, differently proportioned flower. The important differences in the flowers of D. parrasana and D. wrightii, which are indeed similar in facies and no doubt close kindred, have been emphasized in the key to the section and in the accompanying plate.

At Parras, where I have seen the plants only in sterile condition, and in the hill country west of Saltillo, D. parrasana is associated with species of Nama and Anulocaulis known to be obligate gypsophytes, and it is suspected that its apparent rarity is due to its localization on gypseous formations. The gypsum beds of San Luis Potosi are very far from fully explored, and may well yield further populations of this interesting plant.