22 THE FLORA OF THE ALPS 



The species of Treacle Mustard are mostly lowland 

 plants, growing on walls, waste ground, &c. Several 

 species with yellow flowers occur in Southern and West- 

 ern Switzerland, Pyrenees, &c., and are difficult to dis- 

 tinguish from one another, viz. : E. cheiranthoides, L., 

 with small flowers on long stalks ; E. virgatum. Roth., 

 with larger flowers and leaves almost entire ; E. strictum, 

 Wett, with darker flowers and sinuate-dentate leaves ; E. 

 ockroleucum, DC., with linear-lanceolate slightly toothed 

 leaves; Jura; also E. perfoliatum, Crntz. (Coringia 

 orient alis } Rchb.), with white flowers and amplexicaul 

 stem-leaves. E. pumilum, Gaud. (Jielveticum, Koch), is 

 an alpine plant with small fragrant yellow flowers, and 

 sepals very saccate at the base, found at high elevations 

 in the Alps and Pyrenees. 



12. HESPERIS, L. 



Plant pubescent with spreading hairs ; leaves entire ; 

 sepals saccate at the base ; flowers large. Not alpine. 



H. matronalis, L., Dame's Violet, with white or lilac 

 flowers, fragrant in the evening; in hedges, woods, &c., 

 throughout the South. 



Tribe BRASSICE^E. Seed-vessel elongated; seeds in 

 1-2 rows ; radicle incumbent, longitudinally folded or 

 concave. Genera 13-16. 



13. BRASSICA, L. 



Seeds in one row ; sepals erect ; flowers yellow. Not 

 alpine. 



B. campestris, L., the Wild Turnip, is the only un- 

 doubtedly wild species in Switzerland. 



