14. Ranunculus L. (buttercup, crowfoot) (L. Benson, 1948, 1954; Whittemore, 1997)

Plants annual or perennial herbs, sometimes with tuberous roots or stolons. Stems variously erect to prostrate. Leaves alternate and sometimes also in a basal rosette, the blades variously simple to 2–4 times pinnately to palmately or dichotomously lobed, dissected, or compound, the segments usually more than 1 mm wide (if dissected into threadlike or linear segments then plants are submerged or emergent aquatics), the lobes, segments, or leaflets variously shaped. Inflorescences open clusters or panicles of up to 20 flowers at the branch tips or of solitary flowers, these then axillary or terminal. Flowers actinomorphic, perfect. Sepals 3–5, 1–15 mm long, variously shaped, plane or less commonly with a small, saclike appendage toward the base, green, yellowish or occasionally purple, not persistent at fruiting. Petals 3–22(–150) or in a few species sometimes absent, when present 1–27 mm long, plane or slightly cupped, yellow or less commonly white, each with a basal nectary. Stamens prominent but scarcely showy, the anthers yellow. Staminodes absent. Pistils 5 to numerous (to 300 or more), each with 1 ovule. Style absent or present. Fruits achenes, in globose to cylindrical heads or less commonly in small, dense clusters, the body of each fruit, discoid, lenticular, globose, obovoid, or cylindrical, the outer wall thick or papery, smooth to wrinkled, pebbled, or with fine, sharply pointed tubercles, the dorsal surface sometimes winged or keeled, the tip often obliquely beaked (the beak to 4.5 mm long, straight or hooked). Receptacle slightly to moderately elongated at fruiting, glabrous or hairy. About 300 species, nearly worldwide (except in the lowland tropics).

There is a great deal of morphological variation within Ranunculus, and several of the more divergent species groups are sometimes treated as separate genera (Tamura, 1993, 1995; Johansson, 1998). Two of the species in Missouri, R. cymbalaria and R. ficaria, might better be separated from the genus if future research confirms their phylogenetic distinctness (see further discussion under these species).

Collectors should seek to gather specimens that have both flowers and fruits. These are frequently present on the same plant. Vegetative specimens or those just starting to flower should be avoided.