45 2 FLORA. 



or nearly entire. Seeds turgid, minute, in 2 rows in each cell (very rarely in i 

 row). Cotyledons accumbent. [Name unexplained.] About 25 species, of wide 

 geographic distribution. Besides the following, there are about 5 other North 

 American species, natives of the southern and western parts of the continent. The 

 white-flowered species perhaps represent different generic types. 



Flowers yellow. 



Flowers and pods distinctly pedicelled. 



Plants perennial by creeping or subterranean branches. 



Leaves pinnately divided; style very short; naturalized European species. 



i. R. sylvestris. 

 Leaves pinnatifid ; style slender; native western species. 



Pedicels and pods glabrous or nearly so. 2. R. sinuata. 



Pedicels and pods scurfy-puberulent. 3. R. calycina. 



Plants annual or perennial, with fibrous roots. 

 Pods 2-10 mm. long, straight. 



Fruiting pedicels 2-4 mm. long ; stem diffuse. 



Pods linear to oblong, 6-10 mm. long. 4. R. obtusa. 



Pods subglobose, about 2 mm. in diameter. 5. R. sphaerocarpa, 

 Fruiting pedicels 4-8 mm. long; stem erect. 



Stem nearly or quite glabrous; pods linear or linear-oblong. 



6. R. palustris. 



Stem hispid-pubescent; pods globose or oval. 7. R. hispida. 

 Pods 8-14 mm. long, strongly curved upward. 8. R. curvisiliqua. 



Flowers and pods very nearly sessile. 9. R. sessiliflora. 



Flowers white. 



Leaves pinnately divided ; pods linear. 10. R. Nasturtium. 



Leaves simple or the lower pinnatifid ; pods oblong or globose. 



Terrestrial, tall ; leaves crenate, or the lower lobed or pinnatifid. 



ii. R. Armoracia. 

 Aquatic; immersed leaves finely dissected. 12. R. Americana. 



1. Roripa sylvestris (L.) Bess. CREEPING YELLOW WATER-CRESS. (I. F. f- 

 1713.) Perennial, glabrous; stems creeping, branches ascending. Leaves phr 

 natery divided or deeply pinnatifid, petioled, 7-13 cm. long, 2-5 cm. broad, the 

 divisions obovate, or oblong, toothed or lobed; pedicels slender, about 6 mm. long; 

 flowers yellow, 6-io mm. broad; pod linear, 8-12 mm. long; style very short. In 

 low grounds and waste places, Newf. to Mass., Va. and Mich. Adventive or nat. 

 from Europe. Summer. 



2. Roripa sinuata (Nutt.) A." S. Hitchcock. SPREADING YELLOW-CRESS. 

 (I. F. f. 1714.) Perennial, diffuse, glabrous, the branches ascending. Leaves ob. 

 long, lanceolate, or oblanceolate, 5-8 cm. long, 1-2.5 cm - wide, pinnatifid, the lobes 

 linear or oblong, obtuse; pedicels slender, 6 mm. long; flowers yellow, 6-8 mm. 

 broad; pods linear-oblong, often curved, 8-15 mm. long; style slender, 2-4 mm. 

 long. Minn, to S. Dak., Mo., west to the Sierra Nevada. June-Sept. 



3. Roripa calycina (Engelm.) Rydb. SCURFY YELLOW-CRESS. Similar to 

 R. simiata, the leaves rather more deeply pinnatifid; flowers about one-half the 

 size, and pods and pedicels scurfy-puberulent. W. Neb., Wyo. and Mont. Has 

 been referred to R. curvisiliqua. June-Aug. 



4. Roripa obtusa (Nutt.) Britton. BLUNT-LEAVED YELLOW-CRESS. (I. F. f. 

 1715.) Annual or biennial, diffuse. Leaves oblong or oblanceolate, 5-10 cm. long, 

 pinnately divided, or pinnatifid, the lobes obtuse, repand-toothed, or sometimes en- 

 tire; pedicels 2-4 mm. long; flowers yellow, 2-3 mm. broad or less; pods narrowly 

 oblong, or linear, 6-10 mm. long, ascending; style i mm. long. In low grounds, 

 Mich, to Tex., west to the Pacific coast. April-Aug. 



5. Roripa sphaerocarpa (A. Gray) Britton. ROUND FRUITED CRESS. (I. F. f. 

 1716.) Glabrous, 1-3 dm. high. Leaves oblong, obtuse, the lower lyrate-pin- 

 natifid or incised, the upper sometimes nearly entire, petioled or the upper sub- 

 sessile; petioles narrowly margined, somewhat clasping; flowers 2 mm. broad or 

 less; petals yellow, about equalling the sepals; silicic globose, about 2 mm. in di- 

 ameter, about as long as its pedicel; style very short. 111. to Kans., Tex. and 

 Cal. June-July. 



6. Roripa palustris (L.) Bess. MARSH OR YELLOW WATER-CRESS. (I. F. f. 

 1717.) Annual or biennial, erect, glabrous or slightly pubescent, 3-10 dm. high. 

 Lower leaves petioled, 7-17 cm. long, oblong or oblanceolate, pinnatifid, the lobes 

 repand or toothed ; upper leaves nearly sessile, dentate or somewhat lobed ; pedi- 



