12 ALIEN FLORA OF BRITAIN 



Roemeria violacea, Medic. A native of the Mediter- 

 ranean region. It is established as a weed of cultivated 

 ground in some of the eastern counties, and is also on 

 record as a grain alien. 



CRUCIFER^. 



Alyssum calycinum, L. It has been recorded in 

 numerous localities in Britain, frequently in clover or 

 cornfields, never as a wild or even as a naturalised plant. 

 Its power of producing seed in a remarkably short time 

 in light sandy soil gives it a certain degree of per- 

 manence in some cultivated areas. The species is 

 probably one of those introduced with foreign agricul- 

 tural seed. It is a native of dry stony ground in 

 Central Europe, becoming rare and of uncertain status 

 towards the northern coasts in France, Belgium, and 

 Germany. 



Alyssum campestre, L. A native of Southern 

 Europe which has been recorded once as an alien in 

 Cornwall. 



Alyssum hirsutum, Bieb. A somewhat common 

 cornfield weed in the East which has occurred in 

 England among aliens introduced with Syrian barley. 



Alyssum incanum, L. A native of dry places in 

 Central Europe and Siberia, being most abundant in 

 Austria and Bulgaria. The species shows a marked 

 tendency to extend itself along railways and roads. It 

 may indeed be safely assumed that traffic was the cause 



