Dalea nana

  • Title

    Dalea nana

  • Authors

    Rupert C. Barneby

  • Scientific Name

    Dalea nana Torr. ex A.Gray

  • Description

    151.  Dalea nana Torrey

    (Plate CXXXVI)

    Slender perennial herbs (0.5) 1-3.5 dm tall, silky-pilose-pilosulous nearly throughout with fine, straight, narrowly ascending hairs up to 0.6-1.3 mm long, usually densely so, the herbage silvery-gray when fresh becoming greenish-golden in dried specimens, the terete or ribbed, almost glandless stems either simple or branching near base, or distally, or both, the stems and branchlets all monocephalous; leaf-spurs 0.5-1.2 (1.5) mm long; stipules narrowly triangular or subulate, 0.5-2 mm long, pallid becoming dry and papery, stiff but not spinulose, thinly pilosulous, livid-tipped; leaves 1-2.5 (3) cm long, petioled, all or all but a few of the lowest and uppermost 5 (a few exceptionally 7)-foliolate, the margined punctate petiole mostly 4-11 mm long, the rachis shorter, usually (but not always) produced beyond the last pair of leaflets, the leaflets obovate, oblong-obovate, obovate-cuneate, elliptic, or oblanceolate, mostly obtuse and emarginate, sometimes abruptly acute or acuminate above the broad apex, either flat or folded, 3-15 mm long, dorsally carinate and faintly or distinctly punctate, either pubescent or more rarely glabrescent medially to glabrate above; peduncles 0-3.5 cm long, the first spike of branched stems usually pedunculate and the lateral ones sessile or nearly so; spikes variable in density, moderately loose to very dense and conelike, without petals 7-13 (15) mm diam, the villosulous axis 0.5-4 (5) cm long; bracts deciduous late in anthesis or afterwards, subhomomorphic, herbaceous above immediate base, 2.5-5.5 mm long, dorsally pilosulous and often punctate, ciliate; calyx (4.2) 4.5-6.5 (7.5) mm long, densely pilose with straight spreading-ascending spiral hairs up to 1.1-2.5 mm long, the tube 1.9-2.7 mm long, the ribs becoming prominent, pallid and cordlike, the membranous intervals charged with 1 row of 3-4 small transparent glands, the deltate- to triangular-aristate, plumose, reddish or livid teeth 2.2-4.2 (4.7) mm long; petals opening clear yellow, fading brownish, or when dried purplish or pinkish, eglandular, the epistemonous ones perched near middle of androecium 2.7-5 mm above hypanthium; banner (4) 4.4-5.5 mm long, the claw (2.6) 2.8-3.5 mm, the suborbicular-cordate, reniform, or sub- flabellate, obtuse or emarginate blade 1.5-3.2 mm long, (1.5) 2-3.6 mm wide; wings 2.6-4.3 mm long the claw 0.4-0.9 mm, the obliquely ovate blade 2.1-3.7 mm long, 0.9-1.8 mm wide; keel 3.8-6.1 mm long, the claws 0.8-1.5 (1.7) mm, the obovate to oblong-elliptic blades 2.8-4.8 mm long, 1.7-2.8 mm wide; androecium 10-merous, (6) 6.4-10 mm long, the longer filaments free for 1.1-2.3 mm, the pallid anthers 0.4-0.65 (0.7) mm long; pod (of the section) 2.5-3 mm long; seed castaneous, smooth, 1.8-2.2 mm long.

    Variation in D. nana (sens, lat.) has been subject to comment since the earliest period of botanical surveys in the West. The plants differ in stature and mode of branching, in attitude of the stems, in density of the spikes, in shape of bracts, and to some small degree in number or shape or leaflets and pubescence on their upper face. The plant first described is prostrate, irregularly branched, pilose throughout, with relatively loose spikes of flowers subtended by broadly ovate bracts. The calyces of each vertical rank are at least 1 mm distant, with campanulate tube and teeth broadly triangular or deltate at base. The most obvious departure from this standard type is that known as D. rubescens Wats., with erect, simple stems and dense conelike spikes of flowers subtended by narrower, decidedly acuminate bracts. Here the calyces of each rank are pressed close together, wholly concealing the axis even in pressed specimens, and their tube is vase-shaped, with narrower intercostal membranes and narrowly triangular-cuspidate teeth. The habit of extreme D. rubescens is less suggestive of the original D. nana than of some depauperate D. aurea, from which it is distinguished, however, by small rubescent petals. If this were all, two strongly characterized entities could be recognized, but in reality the conelike inflorescence is not confined to the plant with erect monocephalous stems but is found more commonly and over a much wider range on diffusely branching plants habitally simulating typical D. nana. Plants of this latter type, especially when more thinly pubescent, formed the nucleus of Parosela carnescens Rydb., a category found necessary so long as an erect growth-habit was thought to be taxonomically significant. It must be emphasized here that, except for the calycine characters mentioned above, not always sharply definite, the flowers of D. nana, D. rubescens, and P. carnescens are essentially alike. Growth- habit is evidently plastic in the complex, and pubescence, as nearly always in the genus, is unpredictably variable. The one neat racial division that coincides with credible dispersal patterns falls along the line of the two inflorescence types, each with its ordinarily distinctive bracts.