TETKADYNAMIA. SILICULOSA. Q^3 



ei-s small and yellowish; sUique elliptic-oblong-, pubescenf^ 

 Flowering' in May. On ihe gravelly hills of the Missouri, 

 from the river Platte to Fort Mandan, rare. 6. incana: 

 7. Arabis. 

 Almost exclusively an European genus. 



452. ALYSSUM. L. (Gold of Pleasure.) 



Filaments of 2 of the stamina often internal- 

 ly toothed near the base. 8'dide 2-celled, en- 

 tire, acuminated with the style, mostly pubes- 

 cent, subelliptic or globose. 



An obscurely defined g-enus. Most of the species aS 

 in Arabis are furnished with a divided or stellate pubes- 

 cence; stem*! suffruticose as well as herbaceous; leaves 

 generally entire, flowers often yellow, the species with 

 this colour arc said to be those only which produce the 

 denticulated filaments, (an American species with yel- 

 low flowers, and inflated globose pods, is totally desti 

 tute of this distinction and yet unquestionably an Ali;5- 

 sum.) 



Species. 1. A. * dentatum. Stem erect, and herba- 

 ceous, recemes panicula^ „ axillary; radical leaves subrun- 

 cinately toothed, and so. " .v hat asperate, cauline linear- 

 lanceolate, sessile, nearly smooth, and partly entire; sllicie 

 elliptic, compressed, pubescent and contorted, termina- 

 ted by a style nearly its length; peduncle longer than the 

 silicle. Draba Arabisa?is, Ph. not ofMichaux? A plant so 

 distinct, could scarcely bear comparison with Draba inca- 

 na. Obs. Perennial or nearly so; (I have before me sped- 

 mens clothed with the vestigia of 3 years.) Pubescence 

 thin and not communicating any thing of a hoary appear- 

 ance so common in this genus, liairs with only 4 rays, or 

 decussated at right angles. Leaves all lanceolate and acute, 

 those of the stem remote. Seeds brown, elliptic, and 

 compressed, scarcely margined. Flowers not seen. Hab. 

 On the shelvlngs of slate rocks; near Harper's Ferry in 

 Virginia, v. s. In Herb. Muhl. 



2. *ludovicianum. Herbaceous and spreading; argente- 

 ously tomentose; sems numerous, sinnple, angular; leaves 

 linearly spathulate, entire, obtuse, attenuattd; silicles el- 

 liptic, inflated, pubescent. JMyagmm argenteum. Ph. 2. p. 

 434. Hab. On the high hills of the Missouri, and on the 

 shelvings of rocks. Flowering in April and May. Obs. 6 to 

 8 inches high. Perennial. Calix oblong, erect. Petals 

 obovate, entire, golden yellow. Filainenis simple. Pedurr- 

 ck-s about an inch long. SUicle tomeiitose, 2-valved, 2-cel- 



