I; FLOEA OF THE DISTRICT OF COLUMBIA. 165 



Pods not flattened, curved; leaflets less than twice as long as 

 broad, often as broad as long; plants usually floating in water. 



6. SISYMBRIDM. 



Petals yellow. 



Petals 8-15 mm. long. 

 Pods slender, not over 1 mm. thick; upper leaves pinnately divided 



into linear lobes 14. NORTA. 



Pode stout, 2-6 mm. thick; upper leaves with very broad lobes, or 

 sometimes merely toothed . 

 Beak of the pod flattened or angled; pods often hairy, 



21. SINAPIS. 

 Beak of the pod not flattened or angled; pods glabrous. 



22. BRASSICA. 



Petals 5 mm. long or shorter. 



Plants very hairy; pedicels in fruit closely appressed to the stem. 



13. ERYSIMUM. 

 Plants glabrous or nearly so; pedicels spreading or ascending, never 

 closely appressed. 

 Pods less than 1.5 cm. long, on slender pedicels; terminal lobe of the 



leaf much longer than broad 5. RADICXJLA. 



Pods mostly over 3 cm. long, on very stout pedicels; terminal lobe 

 of the leaf often as broad as long 17. CAMPE . 



1. DRAB A L. 

 1. Diaba verna L. Whitlow grass. 



Dry or;noi8t soil; common. March-Apr. Native of Eur. and Asia; widely natu- 

 ralized in N. Amer. 



The plants are very variable, especially in the form of the pods. 



2. KONIGA Adans. 



1. Kouiga maritima (L.) R. Br. Sweet alyssum. 



Waste ground about Washington and Alexandria; obtained at three stations in 

 1915. Native of Eur.; commonly cultivated and sometimes escaping. (Lobularin 

 mnritima Desv.) 



3. CAMELINA Crantz. 



1. Camelina microcarpa Andrzej. False flax. 



Roadsides, grain fields, and waste ground; frequent. May-June. Native of Eur.; 

 ■widely naturalized in N. Amer. (C saliva bi Ward's Flora.) 



4. BURSA Weber. 



1. Bursa bursa-pastoris (L.) Weber. Shepherd's-purse. 



Fields and waste ground; common. March-June. iSTative of Eur.: widely natu- 

 ralized in N. Amer. {Capselln bursa-'pastoris 'Medic . ) 



The leaves are often used as "greens." The common form of this plant has a tri- 

 angular pod, acute at the upper corners. Another form of occasional occurrence 

 has an obcordate pod; the stems are usually lower and tinged with red. 



5. RADICULA Hill. Yellow cress. 



Flowers nearly sessile. Plants annual or biennial, glabrous 1. R. sessiliflora. 



Flowers long-pediceled . 

 Plants perennial, with slender creeping rootstocks; petals about 4 mm. long, bright 

 yellow; leaves mostly pinnate-parted, with narrow segments; pods slender, 

 8-12 mm. long 2. R. sylvestris. 



