244 BRITISH FLOWERING PLANTS chap. 



Xanthium 



The male and female florets are in different heads 

 on the same plant. The female flowers open some time 

 before the males. The males are in several rows ; the 

 females in pairs. The involucre is covered with hooked 

 hairs, which very efi"ectively secure the dispersal of the 

 achenes. 



X. strumarium.— Though generally included in our 

 English lists, this is not a true native. 



Arctium 



A. Lappa (Burdock). — The achenes are large, with a 

 short pappus of stifi" hairs, but the dispersal is perhaps 

 more eff'ectively secured by the strong hooks at the ends 

 of the involucral leaves. The leaves are green above, 

 more or less covered with loose cottony wool beneath. 



Serratula 



S. tinctoria. — Grynodioecious, with, according to 

 Kirchner, intermediate forms. The hairs of the pappus 

 are simple and unequal. This is one of the genera in 

 which there are scales between the florets. Sir J. E. 

 Smith pointed out that the seeds of the female are larger 

 than those of the hermaphrodite form. 



Saussurea 



This genus is closely allied to Serratula, but the 

 hairs of the pappus, at least the inner ones, are feathery, 

 and the anthers have hair-like appendages at their lower 

 ends. The florets are all tubular and complete. 



S. alpina. — The florets are protandrous. The plant 

 is covered with loose cottony hairs. It is an Alpine 

 species, found in North Wales, the Lake district, the 

 Highlands, and Donegal. 



Carduus (Thistle) 



Florets tubular, complete, with scales. Achenes 

 with a pappus, which is sometimes simple, sometimes 



