CRUCIFERAE. 465 



straight, 2-8 cm. long, 2 mm. wide, spreading or ascending. Quebec to Manitoba, 

 the N. W. Terr., Mass., N. Y., 111. and Minn. June-July. 



11. Arabis glabra (L.) Bernh. TOWER MUSTARD. (I. F. f. 1781.) Gla- 

 brous, glaucous above, pubescent at the base, 6-12 dm. high. Basal leaves pet- 

 ioled, 0.5-2.5 dm. long, oblanceolate or oblong, dentate or sometimes lyrate, 

 hairy; stem-leaves sessile, with a sagittate base, glabrous, lanceolate or oblong, 

 acutish; pedicels 4-12 mm. long, erect; flowers yellowish-white, 4 mm. broad; 

 petals slightly exceeding the calyx; pods narrowly linear, 5-8 cm. long, i mm. 

 wide, erect and appressed; style none. In fields and rocky places, Quebec to S. 

 N. Y., Penn., west to the Pacific Coast. Also in Europe and Asia. May-Aug. 



12. Arabis Holboellii Hornem. HOLBOELL'S ROCK-CRESS. (I. F. f. 1782.) 

 Erect, 2-6 dm. high. Lower leaves spatulate or oblanceolate, tufted, petioled, 

 1-5 cm. long, obtuse, entire or sparingly toothed; stem-leaves sessile, erect, clasp- 

 ing; pedicels reflexed or the upper ascending, 6-10 mm. long in fruit; flowers 

 purple or whitish, 6-8 mm. long; petals twice the length of the calyx; pods linear, 

 2-5 cm. long, slightly more than I mm. wide, reflexed; style very short or none. 

 Manitoba and Arctic Am. to Neb., N. Mex. and Cal. Summer. 



34. ERYSIMUM L. 



Annual or biennial herbs, more or less pubescent or hoary, with simple leaves. 

 Flowers mostly yellow. Siliques elongated, linear, 4-angled or rarely terete; 

 valves strongly keeled by a prominent midvein. Stigma lobed. Seeds oblong, in 

 i row in each cell, marginless or narrowly margined at the top; cotyledons incum- 

 bent. [Greek, name of a garden plant, meaning, perhaps, blister-drawing.] 

 About 85 species, natives of the north temperate zone. In addition to the follow- 

 ing, 2 others are found in the Rocky Mts. and one on the Californian coast. 



Flowers 4-8 mm. high. 



Pedicels slender, spreading ; pods very narrow, 1-2.5 cm - long. 



1. E. cheiranthoides. 



Pedicels stout, short ; pods 1.5-5 cm - Jong- 

 Pods 2-5 cm. long, less than 2 mm. thick ; plant green, appressed-pubescent. 



2. E. inconspicuum. 

 Pods 1.5-3.5 cm - l n g> about 2 mm. thick ; plant pale, appressed-canescent. 



3. E. syrticolum. 

 Flowers 16-25 nim. high, conspicuous. 



Stem-leaves linear, grayish strigose ; pods widely spreading. 4. E. asperum, 

 Stem-leaves lanceolate, green ; pods less spreading. 5. E. Arkansanum. 



1. Erysimum cheiranthoides L. WORM-SEED OR TREACLE MUSTARD. 

 (I. F. f. 1783.) Minutely rough -pubescent, 2-6 dm. high. Leaves lanceolate or 

 oblong-lanceolate, 2-10 cm. long, entire or slightly dentate, tapering into a short 

 petiole or the upper sessile; pedicels spreading or somewhat ascending, 6-8 mm. 

 long in fruit; flowers about 5 mm. high; pods linear, obtusely 4-angled, glabrous, 

 1-2.5 cm - l n g' ' ess tnan 2 mm - broad, nearly erect on spreading pedicels; style 

 i mm. long. Along streams and in fields, Newf. to Br. Col., Tenn. Also in 

 northern Europe. June-Aug. 



2. Erysimum inconspicuum (S. Wats.) MacM. SMALL ERYSIMUM. (I. F. f. 

 1784.) Roughish puberulent; stem 3-6 dm. tall. Leaves oblanceolate or linear, 

 2-8 cm. long, obtuse, entire or dentate, the upper sessile, the lower slender- 

 petioled; flowers about 8 mm. high; pedicels stout, about 4 mm. long in fruit, 

 ascending; pods narrowly linear, minutely rough-puberulent, ascending or erect; 

 style very stout, 1-2 mm. long. In dry soil, Ont. and Minn, to Manitoba, Alaska, 

 Kans., Colo, and Nev. July- Aug. 



3. Erysimum syrticolum Sheldon. SAND ERYSIMUM. (I. F. f. 1785.) 

 Similar to the preceding, but pale and finely appressed-canescent, the stems 3-8 

 dm. tall. Leaves firm, linear-lanceolate, entire or denticulate, early falling away; 

 stigma conspicuously 2-lobed; style less than 2 mm. long; pods linear, erect or 

 nearly so on ascending pedicels ; seeds oblong, i mm. long. On dry sandy banks, 

 Minn, to the N. W. Terr. July-Aug. 



4. Erysimum asperum DC. WESTERN WALL-FLOWER. (I. F. f. 1786.) 

 Rough-pubescent or hoary, 2-5 dm. high. Lower leaves lanceolate or oblanceo- 

 late, tapering into a petiole, dentate or sometimes entire ; upper leaves sessile or nearly 



