CRUCIFERAE. II7 



Arabis holboellii Hornem. Much like A. sparsiflora Nutt. but the pu- 

 bescence much finer; pods sharply reflexed; flowers purple or nearly white. 

 Basalt ledges, not rare. 



, Arabis puberula Nutt. Biennial, the whole plant canescent with fine 

 stellate pubescence; stems slender, erect, 10-30 cm. high; leaves all entire, the 

 radical oblanceolate ; cauline linear, sessile and slightly auriculate; pods on 

 slender pedicels, pendulous, 2-4 cm. long; valves 1-nerved below the middle. 

 Blue Mountains, Horner; rare in'our limits. 



Arabis lyallii Wats. Perennial from a branched base, green or somewhat 

 glaucous, glabrous or sparingly pubescent below; stems usually several, 5-10 

 cm. high; radical leaves oblanceolate, acute, with slender petioles; pods straight, 

 erect, 2-5 cm. long; valves 1-nerved below the middle with some smaller veins. 

 An alpine species occurring on the higher peaks of the Blue Mountains. 



160. THELYPODIUM. 



Stout biennial herbs, often succulent; leaves simple, entire, 

 toothed or pinnatifid, often auricled at the base; flowers usually 

 in rather dense racemes; sepals oblong to linear, rather short; 

 style short; stigma entire; pods slender, terete or 4-angled; 

 seeds oblong, in one row in each cell. 



Flowers whitish; leaves fleshy. T. lacinialum. 



Flowers purple; leaves membranous. T. streplanthoides. 



Thelypodiuin laciniatum (Hook.) Endl. Biennial, glabrous and glaucous, 

 rather succulent; stem stout, 50-100 cm. tall, simple or somewhat branched; 

 leaves ovate or lanceolate, irregularly pinnatifid ; terminal lobe largest, coarsely 

 dentate or entire; lateral lobes oblong or linear, entire or dentate, sometimes 

 wanting; racemes dense, 5-40 cm. long; sepals and petals yellowish-white; 

 pod slender, spreading, 5-12 cm. long; pedicels stout, 5-8 mm. long. Walla 

 Walla and Snake River; a common plant in the sagebrush region. 



Thelypodium streptanthoides Leiberg. Leaves green, neither glaucous 

 nor succulent; sepals purple. Crevices of basaltic cliffs along Snake River. 



161. ERYSIMUM. 



Biennial or perennial herbs; leaves rather narrow, entire or 

 toothed, not clasping; flowers often large, usually yellow; pod 

 linear, 4-angled or rarely flattened, not stipitate; valves keeled, 

 with a prominent midrib; seeds oblong, marginless, in one row 

 in each cell. 



Petals 4-5 ram. long; pods 1-2 cm. long. E. cheiranthoides. 

 Petals 16-24 ram. long; pods 5-12 cm. long. 



Seeds quadrangular; leaves entire or dentate. E. asperum. 



Seeds lenticular; leaves entire or nearly so. E. datum. 



Erysimum cheiranthoides L. Erect, branched above, minutely rough- 

 pubescent throughout; leaves lanceolate, acute at each end, entire or minutely 

 dentate, sessile or nearly so; racemes elongate; petals 4-5 mm. long, yellow; 

 pod linear, 4-angled, puberulent, very short-beaked, about 2 cm. long, erect, 

 on spreading pedicels about 1 cm. long. Very sparingly introduced. 



