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Published In: Regni Vegetabilis Systema Naturale 1: 173. 1818[1817]. (1-15 Nov 1817) (Syst. Nat.) Name publication detailView in Biodiversity Heritage Library

Project Name Data (Last Modified On 9/8/2017)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Native


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3. Thalictrum revolutum DC. (wax-leaved meadow-rue, waxy meadow-rue)

Pl. 516 e–h; Map 2388

Plants dioecious (rarely with a few perfect flowers), with rhizomes and slender, nontuberous roots. Stems 50–150(–200) cm long. Stem leaves alternate at few to several nodes; the lower leaves petiolate, the upper leaves sessile or nearly so; well-developed lower leaves 3 times ternately or ternately-pinnately compound, the largest leaflets 1.5–5.5 cm long, mostly longer than wide, oblong to obovate, ovate, or lanceolate, unlobed or 3(–7)-lobed, the lobes rounded to angled or tapered to bluntly or sharply pointed tips, papery or rather stiff in texture, the margins entire or occasionally scalloped, narrowly revolute (the curled-under portion 0.1–0.3 mm wide), the undersurface and stalk usually pubescent with gland-tipped hairs, less commonly glabrous or with only inconspicuous sessile glands, the minor veins often relatively strongly raised from the surface. Inflorescences panicles, their branches glabrous or pubescent with gland-tipped hairs, sometimes only with sessile glands. Flowers all or nearly all imperfect. Sepals 4, 3–4 mm long, white or sometimes pale pinkish- to purplish-tinged. Filaments white or purplish-tinged. Fruits 3–5 mm long, flattened-ellipsoid, not appearing stalked, the beak 2–3 mm long, becoming brittle with age and often shed, the surface glabrous or pubescent with gland-tipped hairs, sometimes only with sessile glands. 2n=140. May–August.

Uncommon in the Mississippi Lowlands division and the western half of the Glaciated Plains, scattered elsewhere in the state (eastern U.S. west to Minnesota and Texas, west sporadically to South Dakota, Nevada, and Arizona; Canada). Banks of streams and rivers, margins of ponds, bases of bluffs, fens, bottomland prairies, bottomland forests, openings and edges of mesic upland forests, and glades; also old fields, fencerows, ditches, railroads, and roadsides.

Glabrous forms of this species have been called T. revolutum f. glabrum Pennell. They do not differ from the typical plant in any other way, and both forms are sometimes found in the same population, so it seems best not to assign a formal name to this variant.

Thalictrum revolutum can normally be distinguished from T. dasycarpum by the form of the hairs found on many parts of the plant: tipped with knob-shaped glands in T. revolutum, nonglandular and tapered at the tips in T. dasycarpum. In most specimens of both species, careful search of the leaflets (especially the bases of the main veins), rachises, inflorescence branches, and achenes will turn up at least a few hairs, but completely glabrous specimens are sometimes found, and they are very difficult to name. M. M. Park (1992) showed that glabrous forms of the two species can be distinguished reliably by multivariate statistical analysis of multiple measurements of the leaflets, filaments, anthers, stigmas, and stalklike bases of the achenes, but these characters are so variable, and the ranges of variation overlap so broadly, that they are useless for routine identification. Steyermark (1963) and Mohlenbrock (1981) tried to distinguish glabrous forms of T. dasycarpum and T. revolutum based on the thickness of the lamina, the revolution of the margin, and the degree to which the minor veins project on the underside of the leaflet, but these characters are also very variable. On average, Thalictrum revolutum does have thicker, more revolute leaves, but many specimens of both species have moderately thick leaflets with veins that project weakly or moderately.



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