184 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Corolla whitish, shorter than the calyx lobea; leaflets more than twice as long as 



broad 5. T. arvense. 



Heads of flowers as broad as long or nearly so. 



Flowers sessile in the head; heads all or mostly sessile 6. T. pratense. 



Flowers stalked; heads all long-stalked. 

 Heads of flowers about 3 cm. in diameter; plants hairy; leaflets much longer 



than broad 7. T. reflexum. 



Heads of flowers 1.5-2.5 cm. in diameter; plants nearly glabrous; leaflets nearly 

 or quite as broad as long. 



Stems erect or ascending, not rooting 8. T. hybridum. 



Stems creeping, rooting at the joints 9. T. repens. 



1. Trifolium agrarium L. Hop clover. 

 Dry fields and waste ground; common. June-Aug. Native of Eur.; widely 



naturalized in N. Amer. 



2. Trifolium procumbens L. 



Dry fields and waste ground; common, May-June. Native of Eur.; widely 

 naturalized in N. Amer. 



3. Trifolium dubium Sibth. 



Dry fields and waste ground; occasional. May-June. Native of Eur.; widely 

 naturalized in N. Amer. 



4. Trifolium incarnatum L. Crimson clover. 

 Roadsides and old fields; occasional, but not persisting like other adventive species. 



May-July. Native of Eur.; sometimes cultivated and escaping. 



5. Trifolium arvense L. Rabbit-foot clover. 

 Dry fields; common. May-July. Native of Eur. and Asia; widely naturalized 



in N. Amer. 



6. Trifolium pratense L. Red clover. 

 Fields and meadows; abundant, May-Aug. Native of Eur. and Asia; widely 



cultivated and naturalized in N. Amer. 



White-flowered plants are sometimes found. Specimens of this species have been 

 reported from our region as T. medium L. 



7. Trifolium reflexum L. Buffalo clover. 

 Low ground along the upper Potomac; rare. May-June. Eastern U. S. 



8. Trifolium hybridum L. Alsike clover. 

 Meadows and waste ground; common. May-Sept. Native of Eur.; widely 



naturalized in N. Amer. 



9. Trifolium repens L. White clover. 

 Fields, meadows, and waste ground; abundant. Flowering throughout the sum- 

 mer. Native of Eur.; widely naturalized in N. Amer. 



Lotus coTniculatus L, bird's-foot trefoil, was collected along the railroad near H 

 Street bridge, Aug., 1915 (./. B. S. Norton). Native of Eur. ; occasionally adventive 

 in N. Amer. 



Amorphafruticosa L., false indigo, was found as an escape from cultivation in Poto- 

 mac Park, May, 1898 (Steele). The species is native farther south and west. 



9. CRACCA L. 

 1. Cracca virginiana L. Goat's-rue. 



Dry fields and woods; common. May-June. Eastern U. S. ( Tephrosia virginiana 

 Pers.) 



The flowers are shown in plate 31. 



