PEA FAMILY 523 



X. Cyathifera. 



Lobes of the involucre toothed. 



Calyx-teeth with elongated, simple or forked, awn-like apices. 



Calyx glabrous, the teeth several-forked. 33. T. cyathiferum. 

 Calyx pubescent, the teeth with a simple awn or the upper tooth with three awns. 



Corolla 6-7 mm. long, shorter than the calyx. 34. T. barbigerum. 



Corolla 10-12 mm. long, exceeding the calyx. 35. T. Grayi. 



Calyx-teeth ciliated, the apex with a short simple apiculation. 36. T. microdon. 



Lobes of the involucre entire, heads small, pubescent. 37. T. microcephalutn. 



XL Involucrata. 



rr»1la rrf»aTn-rr»lnrpd. „ 



38. T. monanthum. 



Perennials. iji.ii i 



Plants villous; heads 1-6-flowered ; involucre inconspicuous; corolla cream-colored, the keel purple 



Plants glabrous; heads large, many-flowered, purple. 



Involucre distinctly lobed, the lobes irregularly toothed. 39. T. fimbnatum. 



Involucre prominently laciniate-toothed, but not lobed. 40. T. spinulosum. 



Annuals. 



Plants glabrous. 



Calyx 10-nerved. 



Keel prominently apiculate; involucre lobed, the lobes several-toothed. 41. T. appendiculatum. 



Keel not apiculate. 



Corolla little exceeding the calyx; involucre divided almost to base into subulate teeth. 

 Calyx glabrous. 42. T. oliganthum. 



Calyx pilose. 43. T - trichocalyx. 



Corolla well exceeding the calyx; involucre lobed, the lobes laciniately toothed. 



Calyx-teeth subulate, entire. 44. T. melananthum. 



Calyx-teeth 3- to several-toothed. 45. T. polyodon. 



Calyx 20-25-nerved. 



Involucre distinctly lobed and the lobes laciniately toothed; calyx-teeth subulate, entire. 



46. T. variegatum. 



Involucre unevenly laciniate-toothed but not lobed; calyx-teeth abruptly attenuate, usually with 

 one or two lateral teeth. 47. T. tridentatum. 



Plants viscid-pubescent and clammy. 48. T. obtusiflorum. 



XII. FUCATA. 

 Flowers large, 10-25 mm. long, cream or yellowish; involucral bracts acute, 6-18 mm. long. 



Calyx-teeth elongated, aristate, 2-3-cleft. 49. T. Gambellii. 



Calyx-teeth entire. 



Three lower calyx-teeth well exceeding the tube; corolla 10-15 mm. long. 50. 7. flavulum. 



Three lower calyx -teeth shorter than the tube; corolla 20-30 mm. long. 51. T. fucatum. 



Flowers 3-6 mm. long, red-purple or ochroleucous. 



Involucral bracts evident, extending beyond the calyx-tube. 



Involucral bracts broad with broad scarious margins, often toothed. 52. T. amplectens. 



Involucral bracts narrowly oblong to oblong, green, scarcely or not at all margined. 



53. 1. stenopnyiium. 



Involucral bracts reduced to a mere ring, no lobes evident. 54. T. depauperatum. 



1. Trifolium procumbens L. Low Hop-clover. Fig. 2656. 



Trifolium procumbens L. Sp. PI. 772. 1753. 

 Chrysaspis procumbens Desv. Fl. Anjou 338. 1827. 

 Amarenus procumbens Presl, Symb. Bot. 1: 46. 1830. 



Annual finely appressed-pubescent, the stems slender, decumbent or ascending, 15-40 cm. 

 long Leaflets 7-15 mm. long, obovate, cuneate at the base, rounded or emarginate at the apex, 

 finely denticulate, the terminal one distinctly stalked; stipules ovate, about 4 mm. long; peduncles 

 6-25 mm. long; heads globose or short-oval, 8-12 mm. high; flowers yellow, rettexed in age, 

 about 4 mm. long ; standard distinctly dilated above, not folded over the pod. 



Native of Europe; sparingly introduced in the Pacific States. May-Sept. 



2. Trifolium dubium Sibth. Shamrock. Fig. 2657. 



Trifolium dubium Sibth. Fl. Oxon. 231. 1794. 

 Trifolium minus Smith, Engl. Bot. pi. 1256. 1799. 

 Chrysaspis dubia Greene, Pittonia 3: 206. 1897. 



Annual very similar to the preceding species, nearly glabrous, the stems straggling or 

 ascending, 5-50 cm. long, branching. Leaflets obovate, truncate or emarginate cuneate at the 

 base the terminal stalked; peduncles 6-25 mm. long; heads nearly globose, 4-6 mm. high; 

 flowers about 3 mm. long, at length reflexed ; standard not dilated, folded over the pod. 



Native of Europe, frequently established in fields and waysides in the Pacific States. Mainly in the Humid 

 Transition Zone. May-June. 



3. Trifolium bifidum A. Gray. Notch-leaved or Pinole Clover. Fig. 2658. 



Trifolium bifidum A. Gray, Proc. Amer. Acad. 6: 522. 1865. 



Annual pale green and glaucous, the peduncles and calyx more or less villous, the stems 

 erect, very' slender, 15-35 cm. high. Leaves long-peduncled ; stipules ovate-lanceolate, entire; 



