⅔× as large, C. intriloba has narrow arrowhead-shaped to elongate ovate leaves with a slightly scalloped margin, with lanceolate-triangular appendages ⅔× as long. C. novae-zelandiae has spade-shaped leaves a bit longer than wide with a round and slightly retuse top and a slightly scalloped margin with appendages half as long, triangular with a blunt tip. Finally C. obtusa also has spade-shaped leaves, with a round and slightly retuse top, but these are about as wide as long and are distinctly scalloped particularly towards the base, and appendages about ¾× as long with a likewise scalloped outer margin and a straight entire inner margin. The actinomorphic flowers lack true petals and nectaries, but the five to nine (sometimes as little as four or as much as thirteen) sepals are distinctly colored yellow (rarely orange or red) to white (sometimes tinged pink or magenta). The shape of the sepals varies between broadly ovate, obtuse, oblong to lanceolate. The number of stamens range between 6–9 in the smallest species (C. dionaeifolia) and 60-120 in the largest (C. palustris) and likewise does the number of carpels range between 2-5 and 5-25. Stamens encircle the carpels and both are planted on a flat floral base. The pollen is yellow and tricolpate except in C. leptosepala ssp. howellii that has pollen with rounded apertures all over the surface (pantoporate) or an intermediate type (pantocolporate), and in C. palustris var. alba, that shows both pollen types. Each carpel contains several ovules set along the ventral suture. These mostly develop into sessile follicles, with elliptic to globular light brown to black seeds without wings, dependent on the species between ½–1½ mm. In C. scaposa follicles are stipitate and in C. leptosepala short stipitate to sessile. C. natans grows floating in fresh waters or on mud, but all other species are terrestrials that grow in moist soils. Key to the species This key makes use of the taxonomic opinions and characters described in Smit (1973). Taxonomy Taxonomic history The oldest description that is generally acknowledged in the botanical literature dates from 1700 under the name Populago by Joseph Pitton de Tournefort in part 1 of his Institutiones rei herbariae. He distinguished between P. flore major, P. flore minor and P. flore plena, and already says all of these are synonymous to Caltha palustris, without mentioning any previous author. As a plant name published before 1 May 1753, Populago Tourn.