Spiranthes tuberosa Raf.

Slender, 1.5–3 dm; root single (unique among our spp.), turbinate, to 6(–10) cm, 4–12 mm thick, sometimes accompanied by the partly decomposed root of the previous year; basal lvs ephemeral, usually ovate, short-petiolate, 2–4(–5) cm, 6–15(–20) mm wide; usually 4–6 bladeless sheaths on the stem; infl 2–8+ cm, its rachis (as well as the whole herbage) glabrous, the ± cylindric fls rather closely set in a single long spiral, 3–5.5 mm, pure white, the lip broadly ovate, distally truncate or sometimes rounded and crisped or slightly erose, puberulent with minute hairs 0.2–0.4 mm on the upper surface, minutely papillate below, the basal callosities less than 1 mm. Acid, usually rather dry soil; Mass. to Fla., w. to Ill., Mo., and Tex. Aug., Sept. (S. grayi; S. beckii, misapplied)