30 ALIEN FLORA OF BRITAIN 



[Sisymbrium officinale, Scop. It is seldom recorded 

 from natural habitats in England or the rest of Europe. 

 There can be no doubt, however, of its indigenous 

 nature on the banks of our larger rivers, and other 

 naturally broken ground.] 



Sisymbrium polyceratium, L. A plant of waste 

 ground in Southern Europe and Western Asia which 

 has occurred about Bury St. Edmunds and in a few 

 other localities in Britain. 



Sisymbrium orientale, L. Native of dry hills and 

 rocky places in the Mediterranean region. It has 

 become a common weed of cultivated and waste ground 

 over a large part of Europe. In Britain, though of 

 comparatively late introduction, it is occasionally very 

 abundant about London and some of our larger towns. 

 In a few localities it was certainly introduced with 

 foreign grain. 



Sisymbrium Sophia, L. Native in the Mediterranean 

 area. According to written records it grows only in 

 artificial localities in Northern Europe, though widely 

 spread and common. In Britain its association with 

 human habitations and operations is usually obvious. 



Sisymbrium strictissimum, L. A native of woods 

 in Central Europe which has been recorded from the 

 banks of the Mersey near Stretford. It does not seem 

 to be a plant of waste or cultivated ground. The record 

 is difficult to explain. I have seen no specimens. 



[Sisymbrium Thaliana, L. It is usually recorded 

 from hedge banks, cultivated ground, walls, and similar 



