Thismia americana N.Pfeiff.
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Authority
Maas, Paulus J. M., et al. 1986. Burmanniaceae. Fl. Neotrop. Monogr. 42: 1-189. (Published by NYBG Press)
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Family
Burmanniaceae
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Scientific Name
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Type
Type. United States, Illinois. Cook Co.: Chicago, bottom prairie swale on E side of Calumet Lake, between Torrence Ave. (at about 11900 South) and Nickel Plate railroad, between Ford plant and Solvay coke plant, sea level, Aug 1912 (fl, fr), Pfeiffer s.n. (holotype, F + alc. not seen, U, alc.; isotype, BM, not seen, MO ale.)
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Synonyms
Sarcosiphon americanus (N.Pfeiff.) Schltr.
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Description
Species Description - Herbs, 0.3-1 cm high including flower, white, hyaline. Roots white, inside browned by mycorrhiza, creeping horizontally just some mm below the surface, consisting of primary and secondary cylindric roots, both with rootcap, 1 mm diam. and variable in length. Stems white, endogenous, terete, 1-1.5 mm diam., covered by 3-6 leaves. Leaves white, appressed, slightly navicular, ovate to broadly ovate, 2-4 mm long, 1.5-3 mm wide, apices acute. Flower upright. Floral tube white, tubular to slightly urceolate, actinomorphic, with six conspicuous and six fainter colored ribs, 7-15 mm long, largest diam. 4-6 mm; throat, circular, ca. 1 mm diam. Shortest tepals a delicate blue-green, inserted at the top of the floral tube, recurved, ovate, 2.5-4 mm long, 1.5-2 mm wide, acuminate to acute, midvein rib-like; in bud filling the gaps between the largest tepals. Largest tepals also blue-green, inserted at the same level as the shorter ones, convergent to slightly connate at the apex, navicular, linear, ca. 5.5 mm long, 1.5-2 mm wide, apex obtuse, the prominent, densely papillate midrib ending in a ca. 0.3 mm long, erect, finger-like appendage. Annulus white, 0.5-1.5 mm wide (extending horizontally from the insertion of the tepals to the throat), ornamented by a blue-green, 0.3-0.5 mm high ring around the throat. Filaments free, inserted in the throat, ca. 1 mm long, ca. 0.5 mm wide. Connectives dilated and adnate to each other by their mediolateral margins to form a tube; each connective linear to oblong, 1.5-2 mm long, 0.5-1 mm wide, apex somewhat curved upwards, rounded to truncate, with a tuft of hairs on top of the thecae; inner surface of tube covered by glandular cells (Pfeiffer, 1918) or little hairs (Schmid, pers. comm.). Thecae attached at the base of the connective, separated from each other, linear, each one ca. 0.5 mm long, 0.1 mm wide. Interstaminal lobes absent. Style cylindric, 1.5-2 mm long, stigmas erect, narrowly ovoid, ca. 1 mm long, basal part papillate, apex curved outwards, hairy. Ovary obovoid, ca. 2 mm high, ca. 1 mm diam. Placentas three, parietal, "swinging free from the ovary walls in the center" (Pfeiffer, 1914). Fruit cup-shaped, 2-3 mm high, including a ca. 0.5 mm high rim, 3-4 mm diam. Seeds ca. 0.5 mm long, ca. 0.2 mm diam., testa thin, hyaline, reticulate.
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Discussion
The close relationship of Thismia americana and T. rodwayi, together making up the section Rodwaya will keep puzzling botanists, because of their disjunct geographic distribution (North America versus Australia). The placentation of this species is not completely clear. In the results of her studies on T. americana Pfeiffer (1914) gives two contradictory figures: 1) a longitudinal section of the ovary of a still closed flower showing two free vertical strings beset with ovules and 2) a cross section, also of a young flower, picturing three parietal stalked placentas. In the text accompanying the figures Pfeiffer stated the three placentas “appear in a central plane as free columns.” This statement confirms the evidence given by figure 1. It is difficult to reconstruct the exact position of the placentas in T. americana from the data provided by Pfeiffer, and the poor condition of the very scarce material does not permit any further dissecting.
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Distribution
United States of America, Illinois. Never found outside the type locality after 1917, probably now extinct (Lucas & Synge, 1978).
United States of America North America| Illinois United States of America North America|