5. Sium frigidum Handel-Mazzetti, Symb. Sin. 7: 719. 1933.
滇西泽芹 dian xi ze qin
Chamaesium frigidum (Handel-Mazzetti) R. H. Shan ex F. T. Pu.
Plants 5–15 cm, slender. Roots fusiform or tubers, rootstock 1–3 cm. Stem sometimes rooting at lower nodes. Leaf blade oblong or lanceolate, 1–4 × 0.5–1 cm, 1-pinnate; pinnae 3–5 pairs, remote, ovate-lanceolate, 2–8 × ca. 4 mm, entire or 1–3-crenellate. Upper leaves much reduced, pinnae 2–3 pairs, linear or reduced to bladeless sheaths. Umbels 1–2 cm across, terminal or lateral; peduncles 2–7 cm; bracts 1, linear-lanceolate, ca. 3 mm, or absent; rays 2–3, 5–10 mm, unequal; bracteoles 1–2, similar to bract, 0.5–1.5 mm, shorter than pedicels, or absent; umbellules 3–5(–9)-flowered; pedicels 2–4 mm. Calyx teeth minute, triangular, ca. 0.15 mm, caducous. Stylopodium flattened; styles reflexed. Fruit ovoid, ca. 2.1 × 2.3 mm; ribs filiform, corky, obscure; vittae 2–3 in each furrow, 4 on commissure. Fl. Jul–Aug; Aug–Sep.
Forests, damp alpine meadows, marshy areas; ca. 3500 m. NW Yunnan (Zhongdian).
This rather little-known taxon is recorded only from a few collections. It was recently suggested that it is conspecific with Apium ventricosum H. de Boissieu (Bull. Soc. France, 53: 425. 1906), but the generic placement of these taxa is still unclear.