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CLASSIFICATION OF ALIEN PLANTS 

 ACCORDING TO ORIGIN. 



T. W. WOODHEAD. Ph.D., F.L.S. 



The publication of Dunn's 'Alien Flora of Britain ' ha.s rexived 

 an interest in these plants. Now that so large a number have 

 been broug-ht tog-ether, along with many details as to their 

 origin and habitats, it may be worth while to notice what is being 

 done on the Continent in classifying the heterogeneous mass ot 

 facts which have for many years been accumulating, in order to 

 bring into prominence the chief points of interest concerning 

 their origin and distribution. Dr. M. Rikli of the Polytechnicum, 

 Zurich, has attempted to do this,* and his scheme of classifica- 

 tion has been fairly generally recognised. It is adopted, with 

 slight additions, by Naegeli and Thellung in their ' Flora of the 

 Canton of Zurich, "t now in course of publication, and below I 

 give a translation, with slight modifications, | of the more 

 important features taken from Part I. of the latter work 

 (Rudeval-und Adventivflora in genetische Gruppen). The 

 names given to the diflFerent groups are not very in\'iting, and 

 some are almost unpronounceable, but the method of grouping 

 is very suggestive, and may be followed with profit in this 

 country, where little advance has been made since Watson's 

 time in this direction. 



The plants here considered belong entirely to the youngest 

 element in our flora, and its existence is bound up with the 

 activity of man. We may therefore call it the ' Anthropophile ' 

 element, and the species belonging to it as ' Anthropophytes.' 



We divide this Anthropophile element into two parts : - 



A. Anthropochores (Rikli), those plants which were not 

 originally wild in the country under consideration, but which, 

 by man's activity, were either purposely or unconsciously 

 introduced, c.o-.^ cultivated plants and herbs. To these may be 

 added in consequence of their occurrence in artificial habitats — 



B. Apophytes (Rikli) species, which were originally native 



* ' Dii' AiUhi-opoclion-ii unci der FoimL-nUn-i.s dcs .N.isliiiliimi piiliistiv 

 (Leyss) D.C." Ber. d. Ziiricli botan. Cicsscll. 1901-3, p. 7'-^"^-: '^•''• 

 Centralbl. xcv. Xr. i. 1904, p. 12. 



\ " Die Flora dfs Kaiitons Zurich. 1 'l\il : I >!<■ Riitk-ral-iiiul .\dvciitiv- 

 tlora, von O. \ac^i-li imd A. Tliclliiiig'. Ziiii( li, 11)05. 



:;: These relate principally to jjroups (> and 7, wlicic I lia\r ventured to 

 make a .sharper ilistinction between them Ihan in the iiii_i;inal. 



N;<turalist, 



