26 CRUCIFER^E. (MUSTARD FAMILY.) 



17. THLASPI, L. Pennycress. 



Pod usually emarginate. Style rather long. Seeds somewhat turgid. — 

 Low glabrous herbs with simple stems ; lower leaves rosulate, entire or 

 toothed, the cauline oblong, auricled and clasping; flowers white or pinkish. 



1. T. alpestre, L. Radical leaves petioled, ovate or obovate : pods 

 acutely margined but not winged. — T. cochlear if or me, DC, of Hayd. Rep 

 1872 ; T. Fendleri, Gray, of Hayd. Rep. 1870. From New Mexico to British 

 America and westward. 



18. LEPIDIUM, L. Peppergrass. 



Low herbs with pinnatifid or toothed leaves and small white flowers. 

 * Petals none: stamens 2 or 4. 



1. L. intermedium, Gray. Erect and branching, puberulent or gla- 

 brous: lower leaves toothed or pinnatifid ; the upper often entire, oblanceolate 

 or linear : pod smooth or rarely puberulent, very shortly winged with some- 

 what divergent obtuse teeth, on spreading pedicels. — L. ruderale of Hayd. 

 Rep. 1870. From Texas to Hudson Bay, and westward to S. California 

 and the Columbia Valley. Forms with small petals are reported from Utah, 

 New Mexico, Texas, etc. 



* * Petals conspicuous : stamens 6. 1 



2. L. montanum, Nutt. Decumbent, branches many from a long some- 

 what woody root, spreading in a circular manner : radical leaves more or less 

 bipinnatifid ; upper leaves trijid or entire: pods indistinctly reticulated, elliptical, 

 slightly emarginate, wingless, with a conspicuous style. — Plains from New Mexico 

 to the British boundary, and in California. 



3. L. alyssoides, Gray. Stems diffuse, branches minutely puberulent : 

 leaves narrowly linear, mucronulate, attenuate at base, very entire, lowest often 

 pinnately lobed : racemes dense, corymbose : pods ovate, shortly winged above with 

 qcutish teeth, scarcely emarginate, with a very short style. — In dry valleys and 

 on hillsides from N. Nevada through Colorado to Mexico. 



4. L. Fremontii, Watson. Glabrous and glaucous, diffusely branched, 

 from a somewhat woody base : leaves linear, entire or sparingly lobed : racemes 

 rather short and few-flowered : pods rounded, abruptly cuneate at base, slightly 

 emarginate with short very obtuse teeth. — Bot. King's Exp. 30, with plate. S. 

 Colorado and through S. Utah to Nevada and California. 



19. PHYSARIA, Nutt. 



Low and stellately canescent plants, distinguished by the inflated, nearly 

 globular cells of the didymous pod. 



1. P. didymocarpa, Gray. Decumbent, diffusely branched: radical 

 leaves broadly spatulate, occasionally lyrate ; cauline oblanceolate : flowers 

 showy : pods deeply emarginate above and below, the cells usually approxi- 

 mate, but sometimes divergent. — From Colorado to British America and 

 westward to the Sierra Nevada. 



i L. sativvm, L., has leaves variously divided and cut, with very numerous round-oval 

 winged pods, and flowers sometimes rose-color. — Introduced in Colorado, Utah, and else- 

 where. 



