Thismia americana N.E. Pfeiffer
Family: Burmanniaceae
Thismia americana image
Morton Arboretum  
Stems white, 0.3-1 cm. Leaves appressed, white, subulate to ovate, 2-4 × 1.5-3 mm. Flowers white with faint blue-green lobes, 8-15 mm; perianth tube slightly urceolate, 6-lobed; outer lobes recurved, ovate, 2.5-4 mm; inner lobes erect, convergent to connate at apex, linear; annulus 0.5-1.5 mm wide; staminal connectives dilated, connate, forming tube proximal to annulus. Capsules 2-3 mm. Flowering summer--early fall. Prairie; of conservation concern; 200 m; Ill. Thismia americana was observed and collected between 1912-1916 from a single site, in a prairie near Chicago, Illinois. It is now possibly extinct. Numerous attempts to relocate the species have been unsuccessful (L. A. Masters 1995); because only a small part of the minute plant is above the level of soil and moss, it could be easily overlooked. This species is believed to be most closely related to T. rodwayi F. von Müller of Australia and New Zealand, presenting a puzzling pattern of distribution (P. J. M. Maas et al. 1986). Some authors (e.g., R. M. T. Dahlgren et al. 1985; Angiosperm Phylogeny Group 1998) have proposed Thismiaceae to include Thismia and allied African and South American genera.

Perennial mycotrophic herb 1.1 - 2.5 cm tall Stamens: six, but fused into a tube (though six stamens easily separated), affixed to raised ring of floral tube (annulus) and hanging downward inside floral tube, with filaments as broad as anthers and connectives. The anthers are arranged on the outer surface of the stamen tube (facing floral tube), and each anther bears two pollen sacs which open lengthwise to disperse the pollen. Mature pollen grains slightly oval, very pale and almost transparent with pale green hue. Pistil: with a single-chambered (but three placentae), short (about 2 mm), inversely egg-shaped, inferior ovary terminated by three fused, short (about 2 mm), fleshy styles and three relatively long, erect lance-shaped stigma lobes. The three placentae separate from the ovary walls early on and thus appear as three separate columns within the ovary cavity. Fruit: one, numerous-seeded, 2 - 3 mm tall, turban- to cup-shaped capsule with flat top, remnant styles in center, and subtended by floral bracts. The seeds are white, tiny (0.4 - 0.5 mm), oblong, and contain very evident endosperm which encloses a single, inconspicuous, few-celled embryo. Fruit begin to appear in first half of September. Flower: one, terminating main axis, white and semitransparent (except for 4 - 6 mm portion above soil line which is more pale bluish or greenish), hairless, small, 0.8 - 1.5 cm tall, 5 - 8 mm diameter, somewhat complexly urn- or lantern-shaped with base of six fused tepals and then two sets of three separate lobes (six total) above. The delicate blue-green color of the aboveground floral parts comes from green oil-like bodies, which absorb color in the blue band of the spectrum. Roots: horizontal, more or less parallel to soil surface, only a few mm deep, white and semitransparent, very small (about 1 mm diameter), varying greatly in length, and storing large supplies of reserve food such as oils and fats. The layer of cells immediately below the root epidermis contains thick-walled, branching, brown mycelia of a coarse fungus. Bracts: few, closely appressed, very reduced and scale-like, white, semitransparent, very thin, hairless, 2 - 4 mm long, 1.5 - 3 mm wide, with pointed tip, and lacking stomata. The three bracts just under the flower are relatively broad and egg-shaped, but the other bracts are much more narrow and awl-shaped.

Similar species: Within the Chicago Region, there are no other species of vascular plants that resemble T. americana. If found, it is more likely to be confused with a fungus due to its ghostly color and small size. Many authorities have proposed that the nearest relative of T. americana is T. rodwayi, which grows in temperate areas of southeast Australia and New Zealand. However, Thiele and Jordan (2002) do not believe they are closely related because there are too many floral morphological differences between them, especially since T. americana lacks appendages on its anther connectives, and both layers of tepals are about the same length. Another temperate species, T. taiwanensis, appears even less closely related since both layers of tepals in that species end in obvious, elongate, tentacle-like appendages, as do several species in Japan and Indonesia.

Flowering: early July to early September

Habitat and ecology: Probably extirpated, found at only one locale in the world, in a low wet sand prairie surrounded by moss in moist soil shaded by typical prairie plants such as black-eyed Susan (Rudbeckia hirta), various goldenrods (Solidago spp.), and swamp milkweed (Asclepias incarnata), although also noted as having been found in the midst of cattails (Typha spp.).

Occurence in the Chicago region: native

Notes: Mycotrophic plants do not produce their own food supply, but are connected to mycorrhizal fungi that harvest carbon and other nutrients from green plants. In T. americana the fungal hyphae are vesicular arbuscular (va) mycorrhizae in the Glomeromycota group. The fungus resides inside layers of root tissue and invaginates the cell walls. In her original description of this unique plant, Pfeiffer (1914) also noted the presence of bacteria, and that crystalline structures of calcium oxalate called raphides are common throughout the plant body. The color-producing oil bodies in the floral tissue are known to not be easily soluble in alcohol (Pfeiffer 1914). This unique little plant is presumed to be insect pollinated, but since it has not been seen since the early 1900's, it is impossible to carry out any studies of pollination biology, genetic and evolutionary relationships, or anything at all. The few plants found by Norma Pfeiffer are the only members of this mostly tropical genus that have ever been found in North America. Unfortunately the site where the plants grew, around Lake Calumet in Chicago, has been severely altered by industrial development and filling in of much of the lake. The original site is likely buried under concrete or some other pavement, and much of the possible habitat nearby has been destroyed.

Etymology: Thismia is an anagram for Thomas Smith, an English plant anatomist and microscopist of early the 1800's. The epithet americana refers to the plant being "of America".

Author: The Field Museum

Stem subterranean, 3-10 mm, with a few minute scales; fl solitary, white and partly bluish-green, partly subterranean, obovoid-oblong, 8-15 mm, inner perianth-segments curved- ascending and connate at the tip. Known only from a wet prairie near Chicago, Ill., and not seen since 1916, the site now destroyed. Late summer. Very similar to T. rodwayi F. Muell., of Tasmania and N.Z.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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