CRUCIFEROUS TRIBE. 59 



* Three other species are found in various parts of 

 Britain : A. stricta (Bristol Eock Cress), which grows 

 on St. Vincent's Eocks, Clifton, and resembles Sisym- 

 brium thalidnum, but has larger flowers ; A. ciliata, 

 which grows at Connemara, Ireland, and Glen Esk, 

 Scotland, and has leaves smooth on both sides, and 

 fringed at the edges ; and A. Tumta, "which grows on 

 old walls in Cambridge and Oxford. The last is a 

 doubtful native ; its flowers are furnished with bracts, 

 and the pods are curved downwards as they ripen. 



16. TURRITIS (Tower Mustard). 



1. T. glabra (Smooth Tower Mustard). The only 

 British species, resembling in habit the preceding genus, 

 from which it is distinguished by having the seeds in 

 two rows instead of one. The root-leaves are toothed 

 and rough, those of the stem entire and smooth ; the 

 flowers are pale yellow. It grows on banks, and is most 

 common in Norfolk and Suffolk. Fl. May, June. 

 Annual. 



17. BARBARE"A (Winter Cress). 



1. B. vulgdris (Common Winter Cress). Lower 

 leaves lyrate, the terminal lobe roundish ; upper obovate 

 toothed. Common in moist waste ground, where it may 

 be readily detected by its smooth, shining, dark green 

 leaves, and its erect angular stem bearing numerous 

 bright yellow flowers. A variety with double flowers is 

 frequent in gardens under the name of Yellow Eocket. 

 FL May August. Perennial. 



* Another species, B. prcecox (Early Winter Cress), 

 is not uncommon in the West of England, and is dis- 

 tinguished from the preceding by its slender habit and 

 narrow leaves, and by being a Biennial. 



