TETRADYNAMIA. SILIC^UOSA. 65 



Leaves entire, except in the commonest species T, 

 Bursa pastoriSf in which the radical ones are pinnatifid, 

 and the silicle moreover triangular and wi.houi marppinj 

 this was the Capsella of Cxsalpinius, and ought perhaps 

 to be separated from this genus. In the other species the 

 capsule varies in form, and the cells are also sometimes 

 1-seeded, consequently there is no precision in the arti- 

 ficial character, th(jugh there is something in the habit or 

 mode of vegetation which appears to distinguish a Thlaspi. 



Species. 1. T. arvense. S. common weed around De- 

 troit, (Michigan Territory.) 2 allincenm. This species 

 sometimes occurs in fields of grain or flax, in such situa- 

 tions 1 have observed it in the state of Ohio. 3. * Uibero- 

 sum. Silicle suborbiculate, ieh ore and compressed; leaves 

 rhomboid-ovate, obsoletely toothed, smooth, and sessile, 

 radical ones upon long petioles; stem pubescent, very 

 sliort and simple; root tuberous and fibrous. Hab. In 

 Western Pennsylvania. Flowering i.a April and .May. 

 Not more than 4 or 5 inches high; flowers rather large, 

 like tho.se of an Arabls, rosaceous. 4. Bursa paatovcs. 



Principally an European genus. 



456. LUNARIA. L, (Moonwort.) 



Silicle entire, elliptic, flat and pedicellate: 

 valves flat, equal with the parallel dissepiment. 

 Two of the leaves of the calix saccate at the 

 base and coloured. 



Leaves simple, the lower ones often opposite. Silicle 

 very large. 



Species. 1. L. aiuma. Beginning to be naturalized 

 in several localities around Philadelpliia; as near Gray's 

 Ferrv, Sec, accompanying Chelidonium majus. 



An European genus, its natural limits iis yet confined 

 to 2 species. 



Order II.— SILIQUOSA. 



457. DENTARIA. L. (Toothwort.) 



Silique springing open elastically and the 

 valves <• nerveless" and revolute. Dissepiment 

 partly fungose. *9%ma cmarginate. CcUixion*, 

 gitudinaliy connivent. 

 t2 



