CETTCIFEE^. 83 



1. Glabrous Rockcress. Arabis perfoliata, Lam. 

 (Turritis glabra, Eng. Bot. t. 777. Brit. Fl. Tower Mustard.) 



An erect annual or biennial, 2 feet or more high, perfectly glabrous except 

 a few soft hairs at the very base, and usually glaucous. Radical leaves 

 spreading but withering early, obovate-oblong, sinuate or pinnately lobed, 

 with a few forked liairs. Stem-leaves oblong-lanceolate, entire, clasping the 

 stem by pointed auricles. Flowers small, white or pale straw-colour. Pods 

 very long and narrow, erect and crowded in a long narrow raceme. 



On banks and roadsides and in open woods, generally distributed over 

 Em-ope and Russian Asia, except the extreme north, in northern America, 

 and in Australia. Irregvilarly scattered over England and southern Scotland, 

 but not recorded from Ireland. Fl. summer. The genus Turritis, wliich 

 formerly comprised many species of Rockcress, is still maintained by some 

 botanists for this species and a few American ones, which have the two 

 rows of seeds rather more distinct than in other RocJccresses. 



2. ToTver Rockcress. Arabis turrita, Linn. 

 (Eng. Bot. t. 178. Towercress.) 



A tall, stiff, erect biennial, approaching in size and appearance to the last 

 species, but rough and somewhat hoary with very short forked or stellate 

 hairs. Radical leaves spreading and stalked, stem-leaves oblong-lanceolate, 

 sessile, and clasping the stem by their rounded auricles, all sHghtly toothed. 

 Flowers small, of a dirty yellowish-white. Pods above 3 inches long, on 

 short erect pedicels, but all curved downwards to one side, forming a long, 

 dense, nodding raceme. Seeds oblong, with a membranous border. 



In hedges, on shady banks, and under rocks, in the hilly districts of cen- 

 tral and southern Europe, and estabhshes itself readily on old walls further 

 north. Indicated at Oxford, at Cambridge, and in Kent, but evidently only 

 introduced into Britain. Fl. spring or early summer. 



3. Hairy Rockcress. Arabis hirsuta, Br. 



( Turritis hirsuta, Eng. Bot. t. 587.) 



A rather stiff erect annual or biennial, attaining a foot or rather more in 

 height, but often shorter, usually simple, and rough with short hairs. Ra- 

 dical leaves spreading, obovate or oblong, and sHghtly toothed ; stem-leaves 

 generally erect, oblong or lanceolate, aU, or at least the upper ones, clasping 

 the stem by short auricles. Flowers small and white. Pods slender, 

 1 to 2 inches long, erect and crowded in a long raceme. Seeds without 

 any wing. 



On walls, banks, and rocks, common in the greater part of Europe and 

 Russian Asia, but not in high northern latitudes. Not an abundant plant 

 in Britain, although occurrmg in numerous localities even in the north of 

 Scotland. Fl. summer. 



4. Fringed Rockcress. Arabis ciliata, Br. 



(Turritis alpina, Eng. Bot. t. 1746.) 



Very near the hairy R., but not above 6 inches high ; the stem usually 

 glabrous, and the leaves only fringed with a few stiff hairs on their edge, the 

 upper ones rounded at the base and not auricled. The flowers are rather 

 larger, and the pods less erect. 



In stony and rocky places, in the mountains of central Europe. In 

 Britain, only by the seaside at Rinville, Cunnemara, m Ireland. Fl. summer. 



