Dalea villosa

Title

Dalea villosa

Authors

Rupert C. Barneby

Scientific Name

Dalea villosa (Nutt.) Spreng.

Description

45.  Dalea villosa (Nuttall) Sprengel

(Plate LVI)

Relatively coarse, densely leafy perennial herbs from long, thonglike orange roots, 2-8(9) dm tall, the erect, incurved-ascending, or diffuse stems greenish or castaneous, ribbed, glandless or almost so, nearly always paniculately branched just (sometimes well) below the central structurally terminal spike, the branches going out into usually smaller spikes, densely villous or villous-tomentulose throughout with fine weak spiral hairs, these on the stem subvertical or slightly retrorse and up to 0.8-1.5 mm (often mixed with shorter, sinuous ones), those on the leaves hardly shorter but loosely ascending to subappressed, the inflorescences likewise densely pilosulous, the foliage greenish-gray to silvery-canescent, the leaflets not or scarcely bicolored, smooth beneath the vesture above, livid-punctate beneath; leaf-spurs 0-1 mm long; stipules linear-caudate or setiform, early dry and fragile, (1.2) 2-6 (7) mm long, commonly livid; intrapetiolular glands 2, minute; post-petiolular glands small but prominent, blunt; leaves short-petioled or subsessile, the primary cauline ones 2-4 (4.5) cm long, with narrowly margined rachis and (4) 5-8 (10) pairs of elliptic to elliptic-oblanceo- late, obtuse and gland-mucronate or acute to short-acuminate, shallowly boat-shaped to loosely folded, dorsally keeled leaflets up to 5-14 (15) mm long, the terminal leaflet short-stalked but smaller than at least some of the lower pairs, the leaves of spurs present in most axils similar but smaller, with mostly 3-5 pairs of shorter leaflets; peduncles 0-1 (2.5) cm long; spikes moderately dense but not conelike, becoming narrowly oblong-cylindric, without petals 7-10 mm diam, the flowers (pressed) appearing ± 3-ranked, the long central (rarely solitary) spike becoming 3-12 (14) cm long, when very long often sinuous or drooping, the lateral ones shorter; bracts deciduous by full anthesis, linear-lanceolate or caudate, (1.5) 2-5.5 mm long, papery, castaneous, dorsally pilosulous up to or almost to the livid sectaceous tip, this commonly but not always surpassing the buds; calyx 2.8-3.8 mm long, densely pilosulous externally with spreading hairs up to 0.7-1.2 mm long or the tube sometimes more shortly hairy, the ribbed and pleated tube 1.9-2.7 mm long, recessed behind banner, the intercostal panels not strongly differentiated in texture, heavily castaneous-flecked, the teeth of ± equal length but dissimilar in form, up to 0.8-1.3 mm long, the 3 dorsal ones lanceolate or subulate, the central pair ovate or deltate, all gland-tipped and sometimes minutely gland-spurred marginally; petals rose-purple, pale pink, or rarely whitish, glandless; banner 4.4-5.6 mm long, the claw 2.1-3 mm, the ovate blade broadly cuneate to truncate or obscurely cordate at base, hooded at apex, 2.3-3 mm long, 2-2.6 mm wide; epistemonous petals 2.6-4.5 mm long, the oblong-oblanceo- late, truncate or obtuse, apically concave blades 2.1-3.8 mm long, 0.9-1.3 mm wide, cuneately contracted into a claw 0.4-0.7 mm long; androecium (5) 5.4-7 mm long, the column 2.2-3 mm, the filaments free for 2.5-4.4 mm, the connective gland- tipped, the yellow or orange-yellow anthers 0.65-0.9 (1) mm long; pod 2.5—3.2 mm long, in profile half-obovate, strongly curved backward, the ventral suture concave, the prow slender but prominulous, the style base excentrically terminal, the valves at very base hyaline, thence papery, densely villosulous, glandless or almost so; seed 2-2.4 mm long.

A species readily recognized by the combination of silvery- or gray-villous vesture, relatively numerous (mostly 5-8) pairs of narrow leaflets, and a loose spike of pale purple or pinkish flowers. In its immense range of dispersal, which extends from the cold prairies of southern Saskatchewan south to the warm-temperate Coastal Plain in eastern Texas, it has become adapted to a wide range of climatic conditions, and being a nearly obligate psammophyte, restricted to islands, of greater and less extent, of dunes, sand bluffs, or sandy woodlands southward, it has become a fine mosaic of small races, variable in stature, density of pubescence, length of hairs, size of calyx and petals, and other small features. On the northern and higher western prairies the stems are usually short, diffuse, and densely villous, and the leaflets are small and crowded. In this region when the root is exposed by shifting of the sand it may sprout adventitious stems, the plant appearing stoloniferous in consequence; but the root-stock is normally determinate, with stems all arising from a thickened crown or short caudex. At lower elevations southeastward the stems tend to become longer, at first diffuse but near the southern limit of dispersal tall and erect, with thinner vesture and larger leaflets. This variation in size and pubescence is nowhere correlated with flower size. The southern extreme from eastern Texas was described as a distinct species, P. griseum T. & G., at a time when only two or three collections of western P. villosum were available for comparison. The original differential characters of P. griseum were thin pubescence and prominently dotted foliage; in reality the foliage of the western type is as strongly punctate, the dots merely being masked by hairs. Time has dissipated the supposed differences and has supplied no reliable substitutes. Rydberg (1920, p. 122) thought P. griseum differed from P. villosum in orientation of the leaves, but this is not detectable in the material I have seen. Turner (1959, p. 160) ascribed to P. villosum a calyx 4-5 mm and to P. griseum a calyx 3-4 mm long, with consequently broader or narrower spikes. Dwarf, densely pubescent plants from the Dakotas yield calyces 3-4 mm long and spikes 7-10 mm diam. The fallibility of these morphological characters was apparent to Wemple (1970, pp. 58-61, figs. 10A, 12A), who nevertheless felt that P. griseum could be maintained as a distinct species so long as emphasis is laid on a syndrome of characters no one of which was entirely reliable, but which generally coincide within a correlated geographic range. Now these conditions are, to my way of thinking, precisely those that characterize vicariant subspecies. In stressing the readily visible but rather superficial differences in stature and pubescence Wemple seems rather to devaluate the multiple similarities and especially the structurally identical flowers. The weakness of the following varietal key is here symptomatic of the situation.