CHAP. XVI THE BRITISH ISLES 359 



Unionid^. 



77. Unio tumidiTs, var. richexsis. Regent's Park. Peculiar form. 



78. „ pictorum, tar. latior. England. 



79. ,, ,, ,, coMPRESSUS. England. 

 SO. ,, margaritifer, var. oliyacetjs. 



81. Anodonta cvgnsea, var. ixcrassata. England. 



82. ,, \, ,, pallida. England, Ireland. 



ESTUARINE OR MARINE PULMONOTRANCHS. 



8.3. As-siMiNEA GRAYAXA. Thames Estuary. 



Feculiaritics of the British Flora.- — Thinking it probable 

 that there must also be some peculiar British plants, but 

 not finding any enumeration of such in the British Moras 

 of Babington, Hooker, or Bentham, I applied to the 

 greatest living authority on the distribution of British 

 plants — the late Mr. H. C. Watson, who very kindly gave 

 me the information I required, and I cannot do better 

 than quote his words : " It may be stated pretty con- 

 fidently that there is no ' species ' (generally accepted 

 among botanists as a good species) peculiar to the British 

 Isles. True, daring the past hundred years, nominally 

 new species have been named and described on British 

 specimens only, from time to time. But these have 

 gradually come to be identified with species described 

 elsewhere under other names — or they have been reduced 

 in rank by succeeding botanists, and placed or replaced 

 as varieties of more widely distributed species. In his 

 British RvM Professor Babington includes as good species, 

 some half-dozen wdiich he has, apparently, not identified 

 with any foreign species or variety. None of these are 

 accepted as ' true species,' nor even as ' sub-sj^ecies ' in 

 the Students Flora, where the brambles are described 

 by Baker, a botanist well acquainted Avith the plants of 

 Britain. And as all these nominal species of Rubi are 

 of late creation, they have truly never been subjected to 

 real or critical tests as 'species.'" 



In my first edition I was only able to name four species, 

 sub-species, or varieties of flowering plants which were 

 believed to be unknown on the continent. But much 

 attention has of late years been paid to the critical ex- 

 amination of British plants in comparison with continental 

 specimens, and I am now enabled to give a much more 



