86 Flora of the Palousc Region 



compressed parallel to the partition; valves nearly flat, nerveless 

 or faintly nerved; seeds few to many, in two rows in the cell, wing- 

 less. 



Flowers white : stems not leafy. D. versa. 



Flowers yellow: stems leafy. " D. nemorosa. 



D. vema L. Annual: stems several, leafless, 5-10 cm. high, simple, 

 nearly glabrous: leaves in a rosette, oblong or oval, toothed or entire, ob- 

 tuse, 4-8 mm. long, pubescent with branched hairs: flowers white, in a loose 

 raceme: petals deeply 2-cleft: pods oblong, glabrous, 4-8 mm. long, shorter 

 than the spreading pedicels. Bluffs of Snake River, not common. 



D. nemorosa L- Annual, the simple stems 5-40 cm. high, leafy and 

 pubescent below: leaves sessile, oblong or ovate, usually dentate, acutish, 

 1-2 cm. long, stellate-pubescent: raceme loose, 3-many-flowered: flowers 

 small, 4 mm. broad: petals yellow, notched, a little longer than the villous 

 sepals: pod oblong, acute, appressed-pubescent or glabrous, about 1 cm. long, 

 much shorter than the spreading pedicels. Stony soil, infrequent. 



138. ATHYSANUS. 



Annual herbs: flowers minute: ovules 3-4, only one maturing: 

 pod orbicular, indehiscent, 1 -celled, 1 -seeded. 



A. pusillus Greene. Stems slender, branched from the base, 10-20 cm. 

 tall, hirsute-pubescent throughout: leaves oblong-lanceolate, acute, usually 

 coarsely dentate, rough-pubescent, 5-30 mm. long: racemes loose, elongate: 

 flowers very small, on curved pedicels: petals linear, minute or wanting: pod 

 orbicular, about 2 mm. in diameter, hirsute, on recurved longer pedicels. 

 Stony soil, rather common. 



139. THYSANOCARPUS. 



Erect and slender sparingly branched annual herbs: flowers 

 minute, white or rose-colored, in elongated racemes: pod mostly 

 pendulous, on a slender pedicel, 1 -celled, indehiscent, disk-shaped 

 or concave, orbicular, winged, 1 -seeded: seed flattened but not 

 winged. 



T. curvipes Hook. More or less hirsute below, glabrous above: stem 

 erect, usually branched above, 30-50 cm. tall: radical leaves oblong, obtuse, 

 dentate, 3-4 cm. long, narrowed at base, with a petiole; cauline sagittate and 

 clasping at base, acute, usually entire, commonly smaller: racemes elongated, 

 loose; pedicels slender, recurved: pods orbicular, ovate or obovate, notched, 

 apiculate by the persisting style, puberulent, 4-6 mm. long, the entire or 

 crenulate wings as broad as the body. Gravelly soils, not rare. 



140. ARABIS. 



Erect annual or perennial herbs: leaves seldom divided, the 

 cauline sessile and usually clasping and auricled at the base: flow- 

 ers white or purple: pod long-linear, compressed parallel to the 



