Erect perennial herbs. Leaves ternately decompound, basal and cauline, the latter alternate. Flowers perfect, polygamous or dioecious, generally small, greenish-white or purplish, panicled or racemed. Sepals 4 or 5, caducous or early deciduous. Petals none. Achenes commonly few, one-seeded, ribbed or nerved, inflated in some species, stipitate or sessile. Stamens 00, exserted. [Derivation doubtful, name used for same plant by Dioscorides.]

A genus of about 85 species, most abundant in the north temperate zone, a few in the Andes of South America, India and South Africa. In addition to the species described below, about 12 others are North American, natives of the Southern States, the Rocky Mountains and the Pacific Coast. Type species: Thalictrum foetidum L.

Flowers perfect.

Stem simple, scape-like; achenes sessile; filaments slender.

1.

T. alpinum.

Stem branched, leafy; achenes long-stipitate; filaments petal-like.

2.

T. clavatum.

Flowers dioecious or polygamous.

Achenes distinctly stipitate.

Roots bright yellow; terminal leaflets not wider than long.

3.

T. coriaceum.

Roots not yellow; terminal leaflets wider than long.

4.

T. caulophylloides.

Achenes sessile or nearly so.

Leaflets waxy-glandular beneath.

5.

T. revolutum.

Leaflets not waxy-glandular.

Filaments capillary or slightly thickened upward.

Leaflets oblong, longer than wide, mostly puberulent beneath.

6.

T. dasycarpum.

Leaflets suborbicular, pale and glabrous beneath.

Achenes thick-walled, indistinctly ridged.

7.

T. vennlosum.

Achenes thin-walled, distinctly ribbed.

8.

T. dioicum.

Filaments club-shaped, often as wide as the anthers.

9.

T. polygamum.

24 Thalictrum Tourn L Sp Pl 545 1753 274

1. Thalictrum Alpinum L. Arctic Or Dwarf Meadow-Rue

Fig. 1932

Thalictrum alpinum L. Sp. Pl. 545. 1753.

Smooth or slightly glandular, 1'-12' high. Leaves small, tufted at the summits of scaly rootstocks, biter-nate; the scapiform stem leafless or I-leaved near the base; leaflets cuneate-obovate or orbicular, firm, 3-5-lobed at the apex, margins revolute; panicle very simple, often racemose; flowers perfect; stamens about 10; filaments filiform, about equalling the sepals; anthers oblong-linear, mucronate; stigma linear; achenes 1 1/2" long, obliquely obovoid, sessile.

Anticosti, Newfoundland and arctic America generally. Also in the Rocky Mountains, and in Europe and Asia. Summer.