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FOC | Family List | FOC Vol. 10 | Fabaceae

159. Trifolium Linnaeus, Sp. Pl. 2: 764. 1753.

车轴草属 che zhou cao shu

Ursia Vassilczenko.

Annual or perennial herbs, glabrous to pubescent. Stems erect to ascending or prostrate. Leaves pinnately 3-foliolate or palmately 3(or 5-9)-foliolate; stipules entire or toothed, partly adnate to petiole; leaflets toothed or entire. Inflorescences axillary or terminal. Flowers sessile or shortly pedicellate, in heads, short racemes, umbels, or rarely solitary; bracts small or absent, often connate into a dentate and membranous involucre. Calyx 5-10[-30]-veined, regular or bilabiate, after flowering sometimes strongly inflated; teeth equal or unequal. Corolla persistent, white, pink, purple, or yellow, sometimes inflated in fruit. Filaments some or all dilated at apex; anthers uniform. Ovary with 1-12 ovules. Legume indehiscent, enclosed by marcescent calyx and petals. Seeds 1 or 2(-9), ovoid to spherical or reniform.

About 250 species: temperate and subtropical Africa, America, Asia, and Europe; 13 species (nine introduced) in China.

1 Stipules almost completely adnate to petiole   (2)
+ Stipules adnate to petiole for 1/2 its length or less   (4)
2 (1) Stem erect; leaflets (3-)5(-9); flowers 20-35, inflorescence capitate.   1 T. lupinaster
+ Stem prostrate or decumbent; leaflets 3; flowers 1-5, inflorescence umbellate   (3)
3 (2) Stem prostrate, thick and short; leaflets with 6 pairs of lateral veins.   2 T. eximium
+ Stem decumbent, thin and long; leaflets with 18-24 pairs of lateral veins.   3 T. gordeievii
4 (1) Petioles slender, shorter than or equal to leaflets; flowers less than 8 mm; ovary stipitate   (5)
+ Petioles, especially in lower leaves, much longer than leaflets; flowers more than 6 mm; ovary sessile   (7)
5 (4) Leaflets all ± sessile; stipules lanceolate, 1-1.5 cm, adnate to petiole for ca. 1/2 their length.   6 T. aureum
+ At least terminal leaflet stalked; stipules ovate to oblong, 4-8 mm, adnate to petiole for less than 1/2 their length   (6)
6 (5) Flowers 5-15; pedicels larger than or equal to calyx tube; corolla 3-4 mm, standard boat-shaped, acute, smooth; leaflets 5-10 mm.   8 T. dubium
+ Flowers 20-40; pedicels smaller than calyx tube; corolla (3-)5-6 mm, standard broadly flattened, emarginate, striate; leaflets 8-16 mm.   7 T. campestre
7 (4) Calyx inflated in fruit, veins reticulate, 2 upper teeth longer than 3 lower teeth.   9 T. fragiferum
+ Calyx not inflated in fruit, veins not reticulate, teeth subequal or lower longest   (8)
8 (7) Flowers pedicellate, bracts present; calyx throat glabrous inside   (9)
+ Flowers ± sessile, bracts absent; calyx throat with a thickened hairy ring inside   (10)
9 (8) Stem prostrate, stoloniferous, rooting at nodes; stipules thin and membranous; calyx teeth shorter than tube.   4 T. repens
+ Stem erect-ascending; stipules herbaceous; calyx teeth longer than or equal to tube.   5 T. hybridum
10 (8) Floral heads sessile or very shortly pedunculate, ovoid to globose, involucrate by stipules of upper leaves.   12 T. pratense
+ Floral heads pedunculate, subglobose to elongate, involucre of small bracts or none   (11)
11 (10) Plants perennial, rhizomatous; stems flexuous; leaf veins arcuate, running into small marginal teeth.   11 T. medium
+ Plants annual, lacking rhizomes; stems upright, straight; leaf veins straight   (12)
12 (11) Floral heads conic to cylindric, 3-6 cm, involucre absent; calyx teeth ± equal; corolla red or pink, rarely white; stipules broad, apex blunt, dark green to purple.   10 T. incarnatum
+ Floral heads ovoid or globose, 1.2-2.5 cm, involucre of small fused bracts; calyx teeth unequal, lower much longer than others; corolla creamy white; stipules narrow, apex attenuate, pale green.   13 T. alexandrinum

  • List of lower taxa


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