jzS ALIEN FLORA OF BRITAIN 



Senebiera pinnatifida, DC. A weed of roadsides 

 and waste ground, especially near the sea in many parts 

 of Great Britain. No earlier record of it is known than 

 Hudson's in 1778, and, indeed, it shows signs of quite 

 recent introduction in most of its stations. Its range 

 may be said roughly to include the Atlantic shores of the 

 •Old and New Worlds, and the Atlantic Islands. In 

 Europe it is usually said to be introduced from America, 

 while in other continents botanists usually derive it 

 from Europe. Sir Joseph Hooker gives a full and lucid 

 summary of its distribution in his Flora Antarctica, 

 p. 241. He considers that it is originally from the New 

 World because the most closely allied species is only 

 found in the Chonos Archipelago. Whichever side it is 

 from, it has almost certainly been originally spread by 

 ships' ballast. 



[Sisymbrium AUiaria, Scop. Native in woods in 

 Britain, but very much more common along hedges 

 about human habitations, though not persisting for long 

 in such situations without an occasional disturbance of 

 the ground.] 



Sisymbrium altissimum, L. A South European 

 weed which has been recorded from waste ground in 

 Britain. 



-Sisymbrium austriacum, Jacq. Native of dry stony 

 hills in Central Europe, becoming a cornfield weed there 

 and in the neighbouring parts of the Continent. It has 

 several times been recorded on waste ground in England. 



Sisymbrium canescens, Nutt. A North American 

 weed, once recorded on waste ground in England. 



