Roadsides, open fields and other weedy situations, usually in damp or wet soil, 

 rare in e. Tex. where recently found in Cass Co., spring; introd. from Eur. and 

 found mostly in the s.e. U.S. 



5. Cardamine pensylvanica Muhl. ex Willd. Fig. 470. 



Biennial or short-lived perennial 2-8 dm. tall; stem usually hispid at base, 

 otherwise glabrous, erect or decumbent and trailing when wholly or partially 

 submersed, simple or much-branched; rosette leaves with 1 to 6 pairs of elliptic 

 to obovate or rounded glabrous leaflets with bases decurrent along or confluent 

 with the rachis, dentate to undulate, the terminal leaflet largest; cauline leaves 

 with membranous leaflets linear-oblanceolate to obovate, their bases oblique and 

 confluent with the rachis, the terminal leaflet usually much broader than the 

 laterals; petals white, 1.5-4 mm. long; stamens 6; siliques narrowly linear, 1-3 cm. 

 long, with slender pedicels 2-15 mm. long, beaked by a tapering style 0.5-2 mm. 

 long; seeds 1-1.5 mm. long. 



In swamps and wet woods, about springs, in seepage areas and along streams in 

 Okla. (Johnston Co.) and Tex. (Fernald), Mar. -Aug.; from Lab. to B.C., s. to 

 Fla., Ala., Ark., (?) Tex. and Oreg. 



6. Cardamine parviflora L. var. arenicola (Britt.) Schulz. Fig. 471. 



Glabrous annual; stems usually erect, simple or branched above, 1-3 dm. tall; 

 leaves pinnatifid to pinnately lobed, petiolate; leaf lobes entire to shallowly den- 

 tate, cuneate at base or with a short petiolule; flowers small, crowded; petals 

 white, spatulate, 2.5-3.5 mm. long; pedicels slender, ascending, 5-8 mm. long; 

 siliques erect, 2-3 cm. long; styles less than 1 mm. long; seeds plump, oblong, 

 0.7-0.9 mm. long; cotyledons accumbent. 



Moist seeps, wet sandy soils and open wet places in wooded areas, ditches 

 and stream banks, e. Okla. (Waterfall) and cen. and e. Tex., Feb.-Apr.; Fla. to 

 e. Can., w. to Ore. and Wash. 



7. Rorippa Scop. Yellow-cress 



Annual to perennial herbs, mostly glabrous or sparingly pubescent; stems 

 usually branched; leaves simple to pinnate or compound; flowers in terminal or 

 axillary racemes; sepals spreading in anthesis; petals yellow or white, small or 

 absent; siliques terete, narrowly cylindrical to globose, sessile; valves nerveless; 

 seeds usually numerous, plump, small, marginless; cotyledons accumbent. 



About 70 species in temperate and subtropical areas of the world. 



Probably all or most of the species, especially the water cress (R. Nasturtium- 

 aquaticiim), are of value as food for wildfowl and wildlife, generally. The herbage 

 of the water cress, used as a salad by man. is known to be eaten by various ducks, 

 muskrats and deer, and it also provides a haven for small aquatic life that, in 

 turn, provide food for fish. Under optimum conditions water cress grows rapidly, 

 often at the expense of most other aquatic vegetation. 



1. Petals conspicuous, white; leaves pinnately compound 



1 . R. Nasturtiiim-aqiiaticum. 



1. Petals yellow if present, minute or absent; leaves entire to pinnatifid but not 



compound (2) 



2(1). Petals exceeding sepals, broadly oblong to obovate; plants perennial with 

 underground rhizomes 2. R. sinuata. 



2. Petals about as long as or shorter than sepals or absent, narrowly oblanceolate 



when present; plants with a taproot (3) 



3(2). Siliques sessile or pedicels less than 2 mm. long; petals absent 



3. R. sessiliflora. 



3. Siliques pedicellate; pedicels 2 mm. long or more; petals present (4) 



971 



