Mirabilis melanotricha
Mirabilis sect. Oxybaphus
black-hair umbrellawort, four o'clock, mountain four-o'clock, Standley's four o'clock
erect or strongly ascending, leafy mostly in proximal 2/3 of plant, openly forked distally, 5–12 dm, pubescent basally with minute curved hairs in 2 lines, spreading glandular-pilose distally.
erect to decumbent, sparsely to densely leafy primarily in proximal 2/3 or throughout.
ascending at 10–60°, progressively reduced toward infloresence;
petiole 0.8–3 cm;
blade bright green, narrowly triangular-ovate to ovate, 3–10 × 0.8–4 cm, ± thin, base acute, obtuse, truncate, or cordate, apex acute to attenuate, or obtuse, often rounded at tip, surfaces glabrous or rarely puberulent.
basal leaves petiolate, blade proportionately broader;
distal leaves sessile or subsessile, blade narrower, margins entire to crisped.
axillary and terminal, few branched, ± evenly forked and open;
peduncle 2–9 mm, spreading glandular-villous, crosswalls of hairs dark purple or black;
involucres blushed with dark violet or black, at least in median region, widely bell-shaped, 3–6 mm in flower, 4–7 mm in fruit, spreading viscid-villous, 40–50% connate, lobes oblong to ovate, apex broadly acute.
axillary and terminal in open or congested, few or repeatedly branched cymes (single in axils, especially in cleistogamous phases);
involucres usually notably accrescent, becoming tan, translucent, prominently net-veined, broadly bell-shaped to saucer-shaped, with (1–)3 flowers inserted at base.
3 per involucre;
perianth bright purple-pink, 0.9–1.2 cm.
perianth broadly funnelform, abruptly flared from narrow tubes, deeply 5-lobed;
stamens 3–5.
dark grayish to blackish brown, sometimes dark, dull, reddish brown, narrowly obovoid, 3–4 mm, spreading-pilose, hairs often apearing loosely shaggy and somewhat tufted, (0.1–)0.2–0.3 mm;
ribs ± same color as sulci, low and round, 0.7–1 times width of sulci, 0.5 times as wide as high, slightly rugose or warty;
sulci almost smooth to slightly rugose or with very low tubercules.
with 5 low ribs, obovoid or narrowly obovate and tapering at both ends, base prominently constricted, apex rounded to nipplelike, surface of fruit slightly rugose to prominently tuberculate on ribs and/or sulci (or ribs and/or sulci without tubercles), glabrous or pubescent, mucilaginous when wetted.
Mirabilis melanotricha
Mirabilis sect. Oxybaphus
The erect habit, bright green and usually glabrous foliage, and dark involucres of Mirabilis melanotricha are distinctive in combination. Once collected and pressed, M. melanotricha becomes yet another “difficult” Mirabilis. In 1911, P. C. Standley noted that this species (as Allionia melanotricha) was one of the most variable in the genus, and in 1918 he submerged it in A. comata, which in the field is a grayish green, clump-forming, glandular-pubescent plant with decumbent-ascending stems. Mirabilis melanotricha occurs in more mesic situations mostly at elevations above M. comata (here in synonymy in M. albida). It intergrades into M. linearis along its northern edge and lower elevations in New Mexico through M. linearis var. decipiens (Standley) S. L. Welsh. In the northeastern portion of its range, it may intergrade with M. nyctaginea; fruits in that region sometimes are slightly more reddish and more tuberculate than usual. Along the eastern portion of its range, it also intergrades into M. albida, as plants become more pubescent and fleshy. B. L. Turner (1993b) noted that M. comata (apparently in the sense of its common usage, as applied to plants here classified as M. melanotricha) might remain distinct from his concept of M. albida, which included C. F. Reed’s (1969) comprehensive M. oblongifolia.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Species ca. 25 (10 in the flora).
Mirabilis sect. Oxybaphus is most diverse in the warm, semiarid regions of North America. Of all the subgroups (i.e., genera in P. C. Standley 1918) within a broadly constructed Mirabilis, sect. Oxybaphus has been the last to be maintained at the generic level by some authors of regional floras. The markedly accrescent involucres of most species make members of the section easily recognized. Standley (1931), in making transfers from Allionia and Oxybaphus to Mirabilis, noted that characteristics supposedly distinctive between segregate genera are not so in South America. C. F. Reed (1969) also used this justification for an inclusive Mirabilis in a treatment of Texas species.
Taxonomy at the species level within the section is unusually problematic. In the introduction to his treatment for Mirabilis, L. H. Shinners (1951b) expressed biological and nomen-clatural problems that plague satisfactory classification. R. W. Cruden (1973) showed cleistogamic and chasmogamic flowers in M. nyctaginea, and self-compatibility in chasmogamic flowers, and R. Spellenberg (1998) mentioned other biological attributes that probably contribute to difficulties. The floral mechanism that Cruden described for M. nyctaginea (stamens and style curling together as the flowers close in late morning) is found in all species and ensures self-pollination. Cleistogamic flowers are found in many other species. Chasmogamic flowers are attractive in some species and are visited by various strong-flying pollinators, among them bees and hummingbirds. B. L. Turner (1993b) used the argument of cleistogamy and hybridization, combined with phenotypic plasticity, to support his concept of a widespread and variable M. albida. Ultimately, some species complexes in the section may be treated more satisfactorily with a number of broadly distributed and variable species, each consisting of a number of infraspecific taxa.
Each species in this section intergrades in some respect with one or more others. Populations of these intergradient types are often highly uniform within. Here, insofar as practicable, species are recognized on combinations of characters that occur within some reasonably extensive geographic region and/or are found in populations that occur in certain rather well-defined ecological situations. Areas of difficult variation are the mountains of the south-western United States and the eastern base of the Rocky Mountains.
Measurements for leaves in the following descriptions are for leaves from mid-stem area. Leaves located toward the base are commonly proportionately broader and on longer petioles; those near and in the inflorescence are proportionately narrower and have much shorter petioles or are sessile.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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