Ranunculus arvensis L.
Annual; roots all fibrous. Stems moderately stout, erect, pubescent above, 10-30-(50) cm tall. Basal lvs subcircular, shallowly 3-5-lobed, 2-4 × 2-4 cm, glabrous; petioles glabrous, 1.5-3 cm long. Cauline lvs 2-ternate; leaflets linear, 2-3-fid, pubescent; uppermost lvs becoming subsessile. Fls 3-7-(15) per stem, 15-20 mm diam. Pedicels erect, pubescent, terete, c. 50 mm long at fruiting. Sepals 5, with sparse long hairs, subacute, 6-7 mm long, spreading, pale yellow. Petals 5, pale yellow, obovate, c. 10 × 6 mm; nectary single, c. 0.5 mm from petal base, covered by a short broad truncate scale. Receptacle hairy. Achenes 5-8, strongly flattened, distinctly bordered, broadly obovate; body 5-7 × 4-5 mm; face with strong long curved spines especially near the margin; beak straight, 2-3 mm long.
S.: Canterbury (Culverden).
S.,W., and C. Europe, N. Africa, S.W. Asia 1880
Pasture.
R. arvensis is most similar to R. muricatus, which also has large spiny achenes, but differs in having spreading sepals, pale yellow petals and deeply divided cauline lvs with linear leaflets. Although R. arvensis is known from only 1 locality at present, it was reported to be well established there.
