84! THE dttrCIEER FAMILY. 



There is some doubt whether the Irish and the Continental plants are the 

 same ; but probably both are mere varieties of the common hairy R. 



5. Thale Rockcress. Arabis Thaliana, Linn. 



(Eng. Bot. t. 901. Sisymbrium, Brit. Fl. Thalecress. Wallcress.) 

 A slender, erect, branching annual, usually about 6 inches high, but 

 sometimes attaining a foot, clothed with short, spreading, stiff hairs, or 

 sometimes nearly glabrous. Leaves mostly radical and spreading, oblong, 

 with a few coarse teeth from i to 1 inch long. Stem-leaves few, small, and 

 sessile. Flowers small and white. Pods on spreading pedicels, in slender 

 racemes, narrow linear, varying from 4 or 5 lines long to twice that length. 

 Seeds small, the two rows blended into one ; the cotyledons placed 

 obhquely, so that the radicle is almost incumbent on the back of one of 

 them. 



On old walls, dry banks, and stony waste places throughout Europe and 

 Russian Asia, extending into northern America. Frequent in Britain. 

 FL early spring, and occasionally aho in summer and autumn. On ac- 

 count of the position of the radicle, this species is referred by some to 

 Sisymbrium, with which it has Uttle else in common. 



6. Bristol Rockcress. Arabis stricta, Huds. 



(Eng. Bot. t. 614.) 

 ■ A perennial, but probably of few years' duration, resembling in some 

 respects the northern R. Radical leaves in a small spreading tuft, pin- 

 nately lobed, and hispid with stiff hairs. Stems about 6 inches high, erect, 

 and nearly simple, with a very few small leaves narrowed at the base. 

 Petals narrow and erect. Pods erect, about an inch long. 



The Continental distribution of this species is uncertain, as the name is 

 often given to plants quite different from ours ; but it appears to be a 

 native of limestone rocks in the mountains of western Europe. In Britain, 

 only on St. Vincent's rocks, near Bristol, where it is getting very scarce, 

 and it will proTaably soon have to be expunged from our Floras. Fl. spring. 



7. Northern Rockcress. Arabis petrsea, Lam. 



{Cardamine hastulata, Eng. Bot. t. 469.) 

 A small perennial, in some respects intermediate between Rockcress and 

 £ittercress. Stems branched at the base, loosely tufted, or shortly diffuse, 

 or almost creeping, but seldom above 6 inches long. Radical and lower 

 leaves obovate or oblong, and stalked, mostly pinnately divided, with the 

 terminal lobe largest, or some of them nearly entire ; the upper leaves few, 

 narrow, almost entire, tapering at the base. Flowers few, considerably 

 larger than in the hairy R., white, or slightly purpUsh. Pods spreading, 

 rather more than half an inch long, the seeds apparently in single rows. 



In the mountains of northern Europe, and m the higher ranges of central 

 Europe, estenduig all across Russian Asia. In Britain, frequent on the 

 higher mountains of northern and western Scotland, and has been found 

 also in Cumberland and North Wales. Fl. summer. 



VI. BITTERCRESS. CARDAMINE. 



Herbs, either annual or with a perennial rootstock, glabrous, or bearing 

 only a few simple hairs ; the leaves pmnate, or, if undivided, on long stalks ; 



