105.  Dalea pulchra Gentry

(Plate XCVII)

Low, stiffly branched shrubs of bushy outline, sometimes flowering precociously as suffrutescent herbs, becoming 5-10 dm tall, the slender, virgate young branches striate, prominently verruculose, and silky-pilosulous with subappressed hairs, the old stems brown or gray, glabrate, fissured, the small, distant leaves silvery-pilosulous or subtomentulose, the leaflets equally pubescent both sides or more densely so above, charged beneath with ± prominent reddish glands; leaf-spurs 0.3-0.8 mm long; stipules triangular-subulate, 0.8-1.5 mm long, firmly chartaceous, livid, puberulent; intra- petiolular glands 0 or minute; post-petiolular glands prominent, obtuse; main cauline leaves (rarely present at anthesis) up to 1.5 cm long, often shorter than the internodes, shortly petioled, with narrowly margined, punctate rachis and mostly 2-3 (4) pairs of obovate to oblanceolate, obtuse or emarginate, bluntly gland-mucronulate, mostly folded leaflets 1.5-5 mm long, the leaves of branchlets similar but smaller, with only 1-2 (3) pairs of leaflets; spikes terminal to main and secondary branchlets (then loosely paniculate) or to axillary, inhibited or subobsolete branchlets (then often forming a narrow spikelike inflorescence of heads), all densely capitate, subglobose or broadly ovate-oblong, without petals 11.5-16 mm diam, the densely pilosulous axis 4-17 mm long; bracts heteromorphic, all deciduous (but sometimes held fast between the crowded calyces) 2-6.5 mm long, the outermost 2-3 ranks imbricated in ascending series, subtending only rudimentary buds, thus forming an involucre of ovate externally velvety-canescent scales, the inner ones linear-lanceolate or -elliptic, longer than the outer ones, pilose externally, all chartaceous, eglandular, glabrous within; calyx (4.5) 4.8-7.2 mm long, densely pilose with spreading-ascending, spiral hairs up to 1.1-2 (2.2) mm long, the tube 2.4-3.2 mm long, deeply recessed behind the banner and the orifice thus oblique, the ribs brown, slender but becoming prominent, the membranous intervals charged with one row of minute (sometimes obsolete), transparent glands, the triangular-aristate, spurred teeth ± unequal, the dorsal one longest, 2-4.2 mm long (0.5 mm shorter to 1.2 mm longer than tube), the ventral pair shortest but hardly broader than the rest, all stellately spreading in age; petals opening bicolored, the banner at first cream-colored, early rubescent, the inner ones pink-purple, elevated 1.2-1.8 mm above the hypanthium rim, the keel sometimes charged with a minute subapical gland but all usually glandless; banner 6-7.5 mm long, the claw 3-4.3 mm, the ovate- or deltate-cordate blade recurved through ± 40°, 2.8-4.2 mm long, 3.4-4.4 mm wide, entire or emarginate at apex, open at base; wings 6-8 mm long, the claw 2-3 mm, the elliptic-oblong blade 4.1-5 mm long, 2-2.6 mm wide; keel 7.8-10.2 mm long, the claws 3-4 mm, the broadly elliptic-obovate blades 5.2-6.8 mm long, 3-3.5 mm wide; androecium 7.5-9 mm long, the longest filament free for 1.8-2.8 mm, the whitish, gland-tipped anthers 0.6-0.7 mm long; pod (seldom seen) ± 2.5 mm long, obliquely obovoid, the style-base terminal but excentric, the valves glabrous and hyaline in the lower half, papery distally, charged along the top with a dense crest of ascending hairs; n = 7 (Spellenberg, 1972, 1973).— Collections: 25 (o).

Grama grasslands, within the lower edge of the oak-belt and below it, along the w. edge of the Sonoran Desert, 900-1350 m (± 3000-4500 ft), forming colonies but local, southern Arizona on the Catalina, Rincon, and Baboquivari mountains, Pima County; near Superior, Pinal County; s. through Santa Cruz and adjoining Cochise County to the forks of Rio Sonora near Cucurpe and Arizpe, Sonora; apparently isolated on Rio Cedros (n. of Tesopaco, at 480 m) in s. Sonora. — Flowering March to May .—Representative: UNITED STATES. Arizona. Pinal: Meebold 15,273 (M); Pima: A. Nelson 11,126a (NY, UC), Rose 11,812 (NY, US), Brass 14,242 (NY); Santa Cruz: Peebles & Fulton 11,550 (NY, US), Gentry 3530 (ARIZ, UC); Cochise: Atwood 2183 (NY). MEXICO. Sonora: R. & M. Spellenberg 3046, 3049, 3052 (NY), Gentry 3045 (ARIZ, F, MEXU, UC).

Dalea pulchra Gentry, Madrono 10: 227, Pl. 14, fig. 1 (map). 1950.— "Type. Soldiers Trail Canyon, near Mount Lemmon road, southern slopes of the Santa Catalina Mountains, Pima County, Arizona, about 4500 feet elevation, April 15, 1946, F. W. Gould and G. T. Robbins 3534..."— Holotypus, ARIZ! isotypus, UC!

The aptly named D. pulchra was collected first by the botanists of the Boundary Survey, by Arthur Schott on Sierra de Pajarito, the present Sierra Pena Blanca (± 15 km w. of Nogales, Santa Cruz Co., Arizona), and by Parry at Agua Prieta, across the present international line from Douglas, Arizona. The specimens were misidentified by Torrey as D. greggii, but as Gentry pointed out in the protologue of D. pulchra, the available material of the two species was at the time insuffient to reveal the true character of either. Features common to D. pulchra and D. greggii as it occurs on the Mexican Plateau are small, silvery-pilose main cauline leaves composed of only 2-4 pairs of leaflets, and short spikes of roseate flowers. In habit they are entirely different. Adult plants of D. pulchra form stiffly branched bushes of round outline 5-10 dm in diameter, the one to several stems arising all from one root; whereas D. greggii has flexuously arching stems that root where they touch the ground and grow together into a low tangled thicket rarely over 3 dm tall but eventually many times as wide. The spike of D. pulchra is very dense, subglobose, and without petals 12-16 mm diameter; the petals are relatively large, the keel-blades mostly 5-7 mm long; and the bracts are pilose externally but glabrous within. By contrast the spike of D. greggii, though short, is not conelike, without petals only 8-11 mm diameter; the petals are smaller, commonly less highly colored, with keel-blade mostly 4-5 mm long; and the bracts are internally silky. Flowering specimens of D. greggii have been collected in nearly every month of the year, but the main bloom occurs between July and December. I have seen no flowering specimens of D. pulchra collected in late summer or fall, and the main bloom is certainly vernal, between March and May. An unusual feature of D. pulchra is the involucre of velvety-pubescent bracts imbricated in about three cycles at the base of the flower spike. These outer bracts are broader and shorter than the inner ones and subtend rudimentary flowers. Finally, as shown by Gentry’s map (1950), the ranges of the two species are notably different, D. pulchra being found only on the Pacific slope of the northern Sierra Madre whereas D. greggii ranges from the eastern piedmont of the Sierra across the Chihuahuan Desert into western Texas and far south and east to Tamaulipas and Oaxaca.

Like several related members of ser. Tuberculatae, D. pulchra presents two aspects at anthesis, one drought-inhibited. Most of the material examined is of this sort, reflecting the commonly dry conditions prevailing during the spring of most years over the range of the species. Here the spikes are mostly borne on brachyblasts issuing from the axils of already fallen primary leaves and in consequence the composite inflorescence forms a sort of virgate raceme of heads, as shown in Plate XCVII. Following the exceptional rains of the winter 1972-3 a series of profusely flowering specimens (cited above) was collected in mid-April by R. and M. Spellenberg on an upper fork of Rio Sonora between Magdalena and Cucurpe. In these plants the lateral branchlets have elongated and a fair number of primary cauline leaves persist well into anthesis. As a result, each main division of the flowering branch is loosely and openly paniculate and the foliage, while still small and sparse in relation to size of the flower-heads, is comparatively ample. The general aspect of these luxuriant examples of D. pulchra recalls D. dorycnioides, a distantly allopatric ally technically separable by the internally silky floral bracts and moreover another species of which the main flowering season begins following summer rains and extends long into the winter.