166 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Plants annual or perennial, with fibrous roots; petals not over 2 mm. long, dull 



yellow or greenish; leaves mostly pinnate-lobed, with broad segments; pods 



thick, 7 mm. long or mostly shorter. 



Plants very hairy, erect; pods almost as broad as long 3. R. hispida. 



Plants glabrous or nearly so; pods twice as long as broad or longer. 



Stems erect; pedicels usually longer than the pods 4. R. palustris. 



Stems spreading; pedicels shorter than the pods 5. R. obtnsa. 



1. Radicuia sessiliflora (Nutt.) Greene. 



Reported by Holm from flats below Chain Bridge. Southern states, north to Va. 

 (Nasturtium scssiliflorum Nutt.; Roripa sessiliflora Hitchc") 



2. Radicuia sylvestris (L.) Druce. 



Open fields and low ground; frequent. May-July. Native of Eur. and Asia; 

 widely naturalized in eastern N. Amor. (Nasturtium syhestre R. Br.; Roripa 

 siflvcstris Bessor.^ 



3. Radicuia hispida (I)esv.) Britton. 



Wet ground along the Eastern Branch. June-Aug. Widely distributed in N- 

 Amer.; also in Eur. (Nasturtium hispidum DC; Roripa hispida Britton; Radicuia 

 ■palustris hispida Robinson.) 



4. Radicuia palustris (L.) Moench. 



Low ground along the Potomac. June-Sept. Widely distributed in N. Amer. 

 in pari naturalized from Eur. (Nasturtium palustrc PC; Roripa palustris Besser.) 



5. Radicuia obtusa (Nutt.) Greene. 



Collected several limes about Washington, the localities not indicated; doubtless 

 adventi ve. Nati ve farther west . ( Nasturtium obtusum Nutt. ; Roripa obtusa Britton.) 



6. SISYMBRIUM L. 

 1. Sisymbrium nasturtium-aqua ticum L. Watercress. 



In streams; occasional. May-autumn. Native of Eur. and Asia; widely natu- 

 ralized in N. Amer. (Nasturtium officinale R. Br.; Radicuia. nasturtium -aquuticum 

 Britten & Rendle.) 



7. ARMORACIA Gaertu., Mey. & Sehreb. 



1. Armoracia rusticana Gaortn., Mey. & Sehreb. Horseradish . 



Occasional by roadsides and in waste ground. Native of Eur.; common iu cultiva- 

 tion and sometimes escaping. (Nasturtium armoracia Fries; Roripa armoracia Hitchc. ; 

 Radicuia armoracia Robinson; A. armoracia Britton.) 



The grated roots furnish the well-known condiment. 



8. NEOBECKIA Greene. 



1. Neobeckia aquatica (Eaton) Britton. Lake cress 



In a pool among the rocks below Great Falls; collected only by Ward, in 1879 and 

 1882. June-July. Eastern N. Amer. (Nasturtium lacustre A. Gray; Roripa ameri- 

 ca»a Britton: Radicuia aqualim Robinson.) 



9. LEPIDIUM L. 



Stem leaves with tapering bases. Plants glabrous or nearly so; pods shallowly 



notched at the top 1, L. virginicum. 



Stem leaves with auricled clasping bases. 



Pods deeply notched, winged; branches of the inflorescence densely and finely 



hairy 2. L. campestre. 



Pods pointed, not winged; branches of the inflorescence glabrous or nearly so. 



3. L draba. 



