Herbs, with (in our species) mostly 3-foliolate, denticulate leaves, and purple pink red white or yellow flowers in dense heads or spikes. Stipules adnate to the petiole. Calyx-teeth nearly equal. Petals commonly persistent, their claws more or less completely adnate to the stamen-tube. Stamens diadelphous, or the tenth one separate for only a portion of its length. Ovary sessile or stipitate, few-ovuled. Pod oblong or terete, often included in the calyx, membranous, indehiscent or tardily dehiscent by 1 suture, or by a lid, 1-6-seeded. [Latin, referring to the 3 leaflets.]

About 275 species, most abundant in the north temperate zone, a few in South America and South Africa. Besides the following, about 60 others occur in the western part of the continent. Type species: Trifolium pratense L.

Flowers yellow. [Genus Chrysaspis Desv.]

Head 6"-9" long; stipules linear; leaflets all sessile.

1.

T. agrarium.

Head 4"-6" long, nearly globose; stipules ovate; terminal leaflet stalked.

Head 20-40-flowered; standard conspicuously striate.

2.

T. procumbens.

Head 10-12-flowered; standard scarcely striate.

3.

T. dubium.

Flowers red, purple, or white.

Head or spike much longer than thick; calyx silky, its teeth plumose.

Corolla crimson, equalling or exceeding the calyx-lobes.

4.

T. incarnatum.

Corolla whitish, shorter than the calyx-lobes.

5.

T. arvense.

Head globose, oval or ovoid.

Flowers sessile, or very nearly so; heads dense, ovoid, oval or globose.

Heads mostly sessile, or nearly so; calyx pubescent.

6.

T. pratense.

Heads always distinctly peduncled.

Calyx-teeth pubescent.

7.

T. medium.

Plant glabrous throughout.

8.

T. Beckwithii.

Flowers pedicelled; heads umbel-like, globose.

Heads 1' in diameter or more; peduncles 1'-3' long.

Prostrate; pubescent; perennial.

9.

T. virginicum.

Ascending; pubescent; annual or biennial.

10.

T. reflexum.

Stoloniferous; glabrous; perennial.

11.

T. stoloniferum.

Heads 6"-9" in diameter; lower peduncles 2'-8' long.

Ascending or procumbent; flowers pink, pinkish, or purple.

Ascending; calyx much shorter than the pink or nearly white corolla.

12.

T. hybridum.

Procumbent; tufted; calyx nearly equalling the purple corolla.

13.

T. carolinianum.

Creeping; flowers white or pinkish.

14.

T. repens.

12 Trifolium Tourn L Sp Pl 764 1753 816