Ranunculus trilobus
Ranunculus sect. Echinella
threelobe buttercup
basal, never tuberous.
erect or reclining, hispid or sometimes glabrous.
erect or decumbent, not bulbous-based, without bulbils.
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;
receptacle hispid;
sepals 5, reflexed, 3-4 × 2 mm, sparsely hispid;
petals 5, 4-5 × 2-3 mm.
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.
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.
ovoid, 8-9 × 6-7 mm;
achenes 30-60 per head, 2 × 2 mm, faces densely tuberculate, glabrous, margin smooth;
beak semicircular, hooked, 0.3 mm.
and lower cauline leaf blades cordate-ovate, 3-foliolate, 5-8 × 3-6(-7) cm, leaflets again cleft or parted, leaflet base obtuse to acute, margins dentate, apex rounded to acute.
Ranunculus trilobus
Ranunculus sect. Echinella
Species ca. 15 (8 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Petals 1–2 mm; achenes finely papillose, papillae terminating in slender hooked hairs or spines; native or introduced. | → 2 |
1. Petals 4–10 mm; achenes coarsely papillose, tuberculate, or spinose, rarely smooth; introduced weeds. | → 4 |
2. Flowers sessile; sepals 3. | R. platensis |
2. Flowers pedicellate; sepals 5. | → 3 |
3. Achenes ornamented on faces and margin, with lanceolate beaks; native of Pacific Slope. | R. hebecarpus |
3. Achenes ornamented on faces but not margin, with deltate beaks; introduced weed, widespread in North America. | R. parviflorus |
4. Sepals spreading; achenes 5–9 in single whorl, the faces and margin long-spinose. | R. arvensis |
4. Sepals reflexed; achenes 10–60 in ovoid or globose heads, the faces papillose to spinose or rarely smooth, margin smooth. | → 5 |
5. Basal leaves compound; achene beak 0.3–0.7 mm. | → 6 |
5. Basal leaves simple; achene beak 1–2.5 mm. | → 7 |
6. Achene faces sparsely papillate or sometimes smooth; petals more than 5 mm. | R. sardous |
6. Achene faces densely tuberculate; petals less than 5mm. | R. trilobus |
7. Achene faces but not margin covered with long spines; beaks 2– 2.5 mm. | R. muricatus |
7. Achene faces but not margin covered with high sharp tubercles or low spines; beaks ca. 1 mm. | R. marginatus |
CA
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