LEGUMINOSAE. 147 



heads or in umbel-like heads; calyx-teeth 5, nearly equal; petals 

 more or less persistent, the claws of all but the standard united 

 more or less below the stamen-tube; stamens 10, diadelphous or 

 the tenth only partly separate; pod small and membranous, 

 1-6-seeded, included in the calyx. 



Heads not subtended by an involucre. 



Flowers pedicelled, in rather loose heads. 



Stoloniferous; flowers white. T. repens. 



Not stoloniferous; flowers pink. T. hybridum. 



Flowers sessile, in dense heads. 



Annual; calyx-teeth plumose, longer than the 



corolla. T. arvense. 



Perennial; calyx- teeth not plumose, shorter than 

 the corolla. 

 Calyx and leaves glabrous; heads usually oblong- 



cylindric. T. douglasii. 



Calyx and leaves pubescent; heads ovoid- 

 orbicular. 

 Flowers red; stipules aristate. T. pratense. 



Flowers whitish; stipules acuminate. T. latifolium. 



Heads subtended by an involucre. 



Involucre deeply cleft, the lobes fringe-toothed; 

 flowers dark-purple. 

 Perennial with creeping rootstocks; heads 10-20 



mm. broad. T. spinulosum. 



Annual; heads S-10 mm. broad. T. variegatum. 



Involucre not deeply cleft, its lobes serrate or entire; 

 flowers white or pink; annual. 

 Glabrous; calyx-teeth slender and branched. T. cyathiferum. 



Pubescent; calyx-teeth subulate, scarious-margined. T. microcephalum. 



Trifolium repens L. White Clover. Perennial, glabrous or sparsely 

 pubescent, with creeping stems, 10-30 cm. long, which root at the nodes; 

 leaflets obovate, obtuse or notched at apex, cuneate at base, denticulate, 1-2 

 cm. long; petioles elongated; stipules narrow, acute; peduncles longer than the 

 leaves; head globose; flowers white, 6-10 mm. long, pedicelled, at length 

 reflexed; calyx-teeth acuminate, shorter than the tube. Everywhere in- 

 troduced. 



Trifolium hybridum L. Alsike Clover. Perennial, erect or decumbent, 

 not creeping, glabrous or nearly so, the stem 30-60 cm. long; leaflets obovate, 

 obtuse or notched, cuneate at base, sharply serrulate, 1-2.5 cm. long; petioles 

 about as long as the leaflets; stipules membranous, ovate-lanceolate, acu- 

 minate; peduncles elongated; heads globose; flowers pink or pinkish, 6-8 mm. 

 long, on slender pedicels, at length reflexed; calyx-teeth subulate, about as 

 long as the tube, much shorter than the corolla. Sparingly introduced. 



Trifolium arvense L. Rabbit's Ear Clover. Annual, erect, somewhat 

 silky-pubescent throughout, 10-30 cm. high; leaflets linear or oblanceolate, 

 obtuse or notched, denticulate near the apex, 1-2 cm. long; petioles mostly 

 shorter than the leaflets; stipules narrow, with long subulate tips; peduncles 

 2-4 cm. long; head oblong, dense, 10-25 mm. long, without an involucre; 

 calyx plumose, the subulate lobes longer than the tube and the pink or whitish 

 corolla. Sparingly introduced. 



Trifolivun douglasii House. (T. aliissimum Dougl.) Perennial from a 

 thick root, erect, stout, glabrous; leaflets linear or oblong, narrowed at both 



