Flora of North America species comparison

Species ca. 25 (10 in the flora).

The species of Ranunculus sect. Flammula are distinctive and easily recognized. Like many amphibious plants, however, they are very variable morphologically, and the species are difficult to define. The taxonomic status of the local endemic species recognized below should be reinvestigated. Depauperate plants of R. glaberrimus (R. sect. Epirotes) may have few or none of the leaves lobed. Such plants were formerly treated under the name R. oreogenes and referred to R. sect. Flammula. In the treatment of R. sect. Flammula below they will key to R. alismifolius var. alismellus, from which they differ in their usually ciliate nectary scales, larger sepals and petals, and larger heads of achenes.

The name Ranunculus lindheimeri Engelmann has been applied to specimens belonging to this section. The name has never been validly published, and its correct application is unclear.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Varieties 3 (3 in the flora).

In Eurasia, this taxon is usually treated as two closely related species. Ranunculus flammula in the strict sense has relatively stout (0.8-3 mm thick) stems that are erect or ascending from prostrate bases, lanceolate to oblanceolate leaves 3-10 mm broad, sepals 3-4 mm, and petals 5-7 × 3-4 mm. Ranunculus reptans has slender (0.2-1 mm thick) stems that are usually prostrate except for the pedicels, leaves linear or filiform, to 2 mm broad, sepals 1-2 mm, and petals 3-5 × 1-2.5 mm. In North America, this distinction holds up relatively well east of the Great Plains, where plants with the characteristics of R. flammula in the strict sense are found in eastern Canada (Newfoundland and northern Nova Scotia) while plants with the characteristics of R. reptans are widespread. In the western part of the continent, however, the situation is much less clear. Collections from the Great Plains and Rocky Mountains resemble R. reptans in most characters, but they often have broader leaves (up to 5 mm broad). Plants from farther west are very confusing; specimens showing the typical morphology of R. flammula in the strict sense and R. reptans are found over a wide area, but most specimens from this area combine the characteristics of the two taxa in various ways. For this reason, it is not possible to separate these taxa at the species level. Three varieties are usually recognized, but further study will probably alter the varietal classification (see comments below, under R. flammula var. ovalis).

(Discussion copyrighted by Flora of North America; reprinted with permission.)