10. Thelypodium paniculatum A. Nelson, Bull. Torrey Bot. Club 26: 126. 1899; Thelypodiopsis paniculata (A. Nelson) O. E. Schulz, Bot. Jahrb. Syst. 66: 99. 1933. TYPE: United States, Wyoming, Lincoln Co., Fossil, 12 June 1898, A. Nelson 4673 (holotype, RM!; isotypes, GH!, MO!, NY!, US!).

Thelypodium sagittatum (Nuttall) Endlicher var. crassicarpum Payson, Ann. Missouri Bot. Gard. 9: 269. 1923. TYPE: United States, Wyoming, Yellowstone National Park, Yellowstone Canyon, 24 Aug 1899, A. Nelson & E. Nelson 6663 (holotype, MO!; isotypes, GH!, NY!, RM!, US!).

     Herbs, biennial or short-lived perennial, glabrous or sparsely to pubescent. Stems (1.4–)2–6.5(–7.5) dm, erect, branched often below and above, solid, glabrous or pubescent. Basal leaves petiole (0.8–)2–4(–6.5) cm, ciliate; blade oblanceolate, rarely spatulate or oblong, (3–)6–15(–22) x (0.6–)1–2.5(–4) cm, entire, glabrous and glaucous; middle and upper cauline leaves (1.7–)2.2–6(–9) × (0.3–)0.5–1.5(–3) cm, sessile, lanceolate to linear-lanceolate, sagittate to somewhat amplexicaul at base, ascending, entire, glabrous. Racemes corymbose, dense, elongated considerably in fruit; flower buds ovate; fruiting pedicels often curved upwards, horizontal to divaricate or rarely divaricate-ascending, slender, slightly flattened at base, 6–11.5(– 17) mm. Sepals ovate to oblong-ovate, erect, (3–)3.5–5(–6) x (1–)1.5–2 mm; petals lavender to purple, spatulate to broadly obovate, (6.5–)8–11.5(–14) x 2.5–5(–6) mm, not crisped, strongly differentiated into blade and claw; claw (2–)2.5–4(–5) mm, slender; filaments tetradynamous, median pairs (3–)3.5–5(–6) mm, lateral pair (2–)2.5–4(–5) mm; anthers ovate to ovate-oblong, 1–2 mm, not circinately coiled, included; nectar glands confluent, subtending bases of all stamens; ovules 20–30 per ovary. Fruits (1–)1.3–3.2(–5) cm x (0.8–)1.5–2.3 mm, erect, terete, slightly incurved or rarely straight, slightly torulose; gynophore stout, 0.5–0.8(–1.2) mm; style cylindrical, (0.5–)1.5–1.7(–3) mm; stigma entire. Seeds plump, (1.3–)1.5–2 x 0.8–1 mm.

Flowering; Jun–Jul.

Habitat: wet sedge meadows, streamsides, river banks.

Elevation: 1800–2750 m.

Distribution: United States (N Colorado, Idaho, Montana, W Wyoming).