3. Description. 



A. General nontechnical description: Spiranthes diluvialis is a perennial orchid with 

 mainly 1 stem 12-50 cm tall, arising from tuberously thickened roots. Its narrow (1 

 cm) leaves can reach 28 cm long, are longest at the base, and persist during flowering 

 (Figure 1). The inflorescence consists of few to many white or ivory flowers 

 clustered in a spike of 3 -ranked spirals at the top of the stem. The sepals and petals 

 are oriented perpendicular to the stem, the lateral sepals often spreading abruptly 

 from the base of the flower, and all sepals are free to the base. The lip petal is 

 somewhat constricted at the median (from U.S. Fish and Wildlife Service 1995b ). 



B. Technical description: Herb, erect, slender to stout, 20-50 cm tall, glabrous below, 

 pubescent above with numerous capitate trichomes. Roots tuberously thickened, up 

 to 1 cm in diameter. Leaves linear-lanceolate, the larger to 28 x 1 .5 cm, basal, 

 usually restricted to the very base of the stem and rapidly reduced upward to 

 sheathing bracts, persisting past anthesis. Spike dense, 3-5 x 1 .2-2.5 cm. Floral 

 bracts ovate, attenuate or acuminate, the lower 9-33 mm long. Flowers 7.5-15 mm 

 long, faintly fragrant with the scent of coumarin, white or ivory, the lip often yellow 

 centrally. Sepals free or connate at the base, the dorsal lanceolate, acute, the lateral 

 broadly spreading to loosely incurved or appressed, linear-lanceolate, acuminate, 

 Petals connivent with the dorsal sepal, linear, acuminate. Lip 7-12 x 2.5-6.8 mm, 

 ovate, lanceolate, or oblong, with a median constriction and occasionally pandurate, 

 the margin entire or dentate toward the apex, crisped, the basal calli prominent, 

 pubescent. Seeds ellipsoidal, monoembryonic (Sheviak 1984). 



C. Local field characters: Spiranthes diluvialis is characterized by whitish, stout, 

 ringent (gaping at the mouth) flowers, with slender, elongate petals and sepals that 

 are white to ivory-colored and free to the base (Figure 2). The lip is exposed in 

 lateral view; with an oval to lance or oblong outline, a marked median constriction, 

 the base usually dilated, the venation mostly parallel, typically with some branching 

 divaricating in the lower half, and with crispy-wavy margins. The upper stem is 

 sparsely to densely pubescent, the longest hairs are longer than 0.19 mm, and the 

 glands are obviously stalked. The persistent leaves are mostly restricted to the base 

 of the stem, reduced to bracts above (adapted from U.S. Fish and Wildlife Service 

 1995b, Wyoming Technical Plant Committee 1995). 



By comparison, S. romanzoffiana has petals and sepals which usually curve in the 

 shape of a hood on top. It has a more deeply constricted lip petal, and more densely 

 congested and shorter spikes compared to S. diluvialis. Its numerous leaves often 

 extend up the lower stem (Figure 2). It also differs from Spiranthes diluvialis in 

 Montana in that it occupies mainly montane settings rather than arid bottomlands, 

 though it has been noted in the Eureka Plains of northwestern Montana (Lesica pers. 

 commim.) and in open canyon settings on the upper Madison River in southwestern 

 Montana (pers. obs.). Comparison with similar species is presented in Table 1 . 



