Flora of North America species comparison

basal, never tuberous.

erect or decumbent, not bulbous-based, without bulbils.

nearly erect, hispid, base not bulbous.

basal and cauline or sometimes only cauline;

basal and lower cauline leaves similar, petiolate, blades undivided, lobed, or compound, segments lobed or unlobed, margins entire or dentate.

2-16-flowered cymes (cymes sometimes sympodial, then flowers seemingly inserted opposite bracts).

pedicellate (sessile in R. platensis);

sepals deciduous soon after anthesis, 5 (3 in R. platensis);

petals yellow (sometimes absent in R. hebecarpus);

nectary scale attached basally, free from petal for at least 1/2 its length, forming flap covering nectary, glabrous, free margin entire;

style present.

pedicellate;

receptacle pilose;

sepals 5, reflexed, 3-8 × 1.5-3 mm, pilose;

petals 5, 7-10 × 4-8 mm.

achenes, 1-locular;

achene body discoid, strongly flattened, 3-7 times as wide as thick, not prolonged beyond seed;

wall thick, spiny, tuberculate, or papillose (sometimes smooth in R. sardous);

margin low or high, broad or narrow ridge;

beak much shorter than achene body.

globose or ovoid, 5-8 × 6-7 mm;

achenes 15-35 per head, 2-3 × 2-3 mm, faces sparsely papillate or sometimes smooth, glabrous, margin smooth;

beak oblong to deltate, curved, 0.4-0.7 mm.

and lower cauline leaf blades ovate to cordate, 3-foliolate, 2-6 × 2-6 cm, leaflets again parted, leaflet base truncate to acute, margins crenate-dentate to crenate-lobulate, apex rounded to obtuse.