Dalea choanosema

  • Title

    Dalea choanosema

  • Author(s)

    Rupert C. Barneby

  • Scientific Name

    Dalea choanosema Barneby

  • Description

    109.  Dalea choanosema Barneby

    (Plate CII)

    Perennial herbs with slender, erect, purplish-castaneous, sparsely gland-tuberculate stems up to 1 m tall, paniculately branching distally, rather densely but inconspicuously puberulent with fine, subappressed hairs up to 0.1-0.2 mm long, the foliage green, the leaflets glabrous or nearly so above, at least thinly pubescent and tuberculate beneath; leaf-spurs 0.5-1 mm long; stipules slenderly subulate, livid, becoming dry and fragile, 0.8-1.5 mm long; intra- and post-petiolular glands small but prominent, hemispherical, glabrous; main cauline leaves ± 2-2.5 cm long, shortly petioled, with slender, very narrowly margined rachis and 4-5 pairs of broadly oblanceolate to nearly obovate, obtuse or truncate-emarginate, flat leaflets, those of the terminal trefoil largest, up to 5-6 mm long, the rameal leaves similar but smaller, some upper ones with only 2-3 pairs of leaflets up to 2.5 mm long; peduncles terminal to main divisions of the panicle and to all the branchlets, 1-5 cm long; spikes moderately dense, the calyces subcontiguous but not wholly concealing the puberulent axis, without petals or androecia ± 7 mm diam, the flowers spreading-ascending, the axis 1-3 cm long; bracts persistent, broadly ovate abruptly acute or short-acuminate, 1-1.5 mm long, puberulent and gland-tuberculate dorsally, glabrous within; calyx ± 3.8 mm long, thinly pilosulous externally with subappressed hairs up to 0.25 mm long, the somewhat oblique orifice more densely ciliolate, the tube constricted near base, thence campanulate, 2.6-2.8 mm long, angulate by the scarcely prominent ribs, the firm intervals charged with 3-5 glands not vertically ranked into one series, the obtusely gland- tipped teeth unequal, the dorsal one longest, ovate, 1-1.2 mm long, the rest shorter, deltate-ovate, shortly acute, the ventral pair broader than long; petals at first bicolored, the banner opening whitish except for a purple tip, finally rubescent, its blade sparsely gland-sprinkled in the eye, the inner ones bright purple, glandless, elevated only 0.4-1.2 mm above hypanthium rim; banner ± 6 mm long, the claw 2.5 mm long, dilated upward, the erect, suborbicular, emarginate blade ± 4 mm long, nearly 5 mm wide, united across the base into a deep cornet; wings 5.8 mm long, the claw 1.6 mm, the oblong-ovate blade ±4.6 mm long, 2.3 mm wide; keel 7.5 mm long, the claws 2.4 mm, the broadly elliptic blades 5.5 mm long, 3 mm wide; androecium 10-merous, 7.8 mm long, the longest filament free for 2.7 mm, the gland-tipped anthers 0.7 mm long; pod obliquely deltate in profile, 2.5 mm long, 2.5 mm wide, the style-base latero- terminal, the sutures filiform, the valves membranous in the lower half, thinly papery and pilosulous distally, the subhorizontal leading edge livid; seed it 1.8 mm long.— Collections: 1 (typus).

    Pine-oak woodland, on igneous bedrock, ± 2250 m (7500 ft), known only from the Sierra Madre del Sur near Chilpancingo, Guerrero. — Flowering November-December.

    Dalea choanosema (with funnel-shaped banner) Barneby, sp. nov., D. bicolori H. & B. ex Willd. affinis, praesertim caulibus herbaceis elatis virgatis ultra medium laxe panicu- latim ramosis, idcirco habitu toto absimilis; a D. bicolori var. naviculifolia, quoad calycis forma praesimili, foliolis pauci (4-5 nec 5-9)-jugis, corolla majori, vexillique lamina glandulis conspersa ulterius distat. — Guerrero : Cerro de Alquitran, cerca de Mazatlan, municipio de Chilpancingo, Dec. 6, 1966, Jerzy Rzedowski 23,634. — Holotypus in herb. Inst. Politecnico Nac. Mex. (ENCB).

    This species seems close to D. bicolor sens, lat., from which it differs principally, and somewhat precariously, in habit of growth. Elsewhere in these pages I have repeatedly emphasized the facility with which daleas known to become eventually shrubby or even subarborescent can bear flowers toward the end of their first season, appearing annual or, if perennial, herbaceous; and I have found it necessary to reduce to synonymy several species originally defined in terms of duration of the root. Obviously I have been speaking here of individual plants that differ in stature due purely to age or to age modified by environmental circumstances. At the same time there are many daleas characteristically fruticose, just as there are many obligately herbaceous, dying back each year to a root- crown or caudex at level of the soil. I have seen a few seedling individuals of D. bicolor already in flower, but the mature plant of all its many forms becomes shrubby or suffruticose by the end of the first season. Thus I feel confident that D. choanosema, which has slenderly virgate, distally paniculate, herbaceous stems that have reached a height of a meter within the current year, cannot be accomodated within D. bicolor, even though I have found no important differential character where one would prefer to see them, in structure of the leaf or fruit. The form of D. bicolor that most nearly suggests D. choanosema is the Oaxacan D. bicolor var. naviculifolia; the two can be compared at Plate CII. The figures do not show the differences in habit, but the differences in flower-size and number of leaflets are instantly evident. The banner of D. bicolor, usually glandless, is exceptionally tipped with a small gland, but never gland-sprinkled about the eye of the blade. As compared with that of D. bicolor, the banner blade of D. choanosema is not only gland-sprinkled, but exceptionally ample, more erect, and contracted at base into an exceptionally deep and wide funnel-shaped well.

    The one known locality of D. choanosema lies well outside the known range of D. bicolor. The latter, principally a species of the Mexican plateau, extends down the Sierra Madre Oriental into Puebla and on into central Oaxaca. It reaches the Lerma valley in Michoacan, and in the same state and adjoining Mexico extends into the Neovolcanic belt, reaching the edge of the Balsas depression on the southern flanks of Nevado de Toluca. There is no record of D. bicolor from Sierra Madre del Sur, where it may perhaps be represented by D. choanosema.