Aulacospermum Ledebour; Hymenidium de Candolle; Hymenolaena de Candolle; Pterocyclus Klotzsch.

Herbs perennial, rarely biennial. Root crown often surrounded with fibrous remnant sheaths. Stems erect, sometimes shortened. Leaves 1–4-pinnate or ternate-pinnate; ultimate segments serrate to incised or pinnate. Umbels terminal and lateral; bracts several, entire or pinnate, margin usually white scarious; rays often extending in fruit; bracteoles numerous, scarious, sometimes white margined. Calyx teeth conspicuous or obsolete. Petals oblong to broad-ovate, white or purple-red, base clawed, apex narrow, inflexed. Stylopodium conic or short-conic. Fruit oblong to broad-ovoid, slightly flattened laterally, glabrous, often with numerous, shining tubercules; ribs prominent and acute, sometimes undulate, cristate or narrowly winged; vittae 1(–3) in each furrow, 2(or 4 or 6) on commissure. Seed face concave. Carpophore 2-parted.

This is a widespread, heterogeneous genus of complex and controversial taxonomy. Russian authors delimit Pleurospermum sensu stricto by only two species (the type, P. austriacum Linnaeus, and P. uralense), referring the other species to Aulacospermum, Hymenidium, Hymenolaena, Physospermopsis, and Pterocyclus. Other morphologically similar genera, where generic boundaries become indistinct, include Trachydium and Pseudotrachydium (Kljuykov et al.) Pimenov & Kljuykov. A full discussion of the Russian classification of Pleurospermum is presented by Pimenov and Kljuykov (Feddes Repert. 111: 499–515, 517–534, 535–552. 2000). As yet, this rather radical classification has not gained widespread acceptance, and the proponents admit that this is a taxonomic hypothesis, and (particularly for some groups) a more natural classification will only be possible following critical revision in the field and herbarium. A traditional treatment is adopted for the following account, with due influence from the work of the Russian taxonomists.

The following species have been described from Chinese material, but are imperfectly known as no specimens have been seen or the specimens are inadequate.

Hymenidium pachycaule Pimenov & Kljuykov (Edinburgh J. Bot. 53: 275. 1996), described from NW Gansu (“Lienhuo Shan,” J. F. C. Rock 12703, holotype, E; isotype, NAS). It is possibly referable to Pleurospermum, but further research is required.
Pleurospermum albimarginatum H. Wolff (Repert. Spec. Nov. Regni Veg. 21: 243. 1925), described from W Sichuan (“Tongolo,” J. A. Soulié 2618, holotype, P).
Pleurospermum grandifolium H. Wolff (Repert. Spec. Nov. Regni Veg. 21: 244. 1925), described from W Sichuan (“Tatsienlu” [Kangding], J. A. Soulié 2182, holotype, P). It has possible affinities with P. benthamii.
Pleurospermum microphyllum H. Wolff (Repert. Spec. Nov. Regni Veg. 21: 242. 1925), described from W Sichuan (“Tongolo,” J. A. Soulié 2605, holotype, P).
Pleurospermum microsciadium H. Wolff (Repert. Spec. Nov. Regni Veg. 21: 241. 1925), described from W Sichuan (“Tongolo,” J. A. Soulié 2614, holotype, P).
Pleurospermum souliei H. Wolff (Repert. Spec. Nov. Regni Veg. 19: 309. 1924), described from W Sichuan (Kangding, J. A. Soulié 2196, holotype, P).

About 50 species: N Asia, E Europe, and especially diverse in the Himalayan region and W China; 39 species (22 endemic) in China.

(Authors: Pan Zehui (潘泽惠); Mark F. Watson)