INTRODUCTION. . XXIU 



as adventitious, because it is well known that plants will, in 

 particular districts, where soil, climate or other causes are ad- 

 verse to their increase, continue so scarce as to be reduced to 

 a numerical minimum little short of absolute extinction, and 

 yet pertinaciously maintain their footing if undisturbed. Of 

 the former part of this proposition at least, Cephalanthera gran- 

 diflora and Euphorbia Peplis present, in this island, notable ex- 

 amples ; a solitary specimen of each of these having alone been 

 picked, but in situations so exactly conformable to their natu- 

 ral places of growth in other parts of the country, as scarcely 

 to afford ground for their rejection on the score of their pau- 

 city, whilst no exception can be taken to the species them- 

 selves. It is indeed hardly credible that an orchideous plant 

 like the former could have been purposely introduced,* though 

 it is just possible that the latter may have been transported by 

 the waves from the coasts of Devon or Cornwall to the beach 

 at Sandown. 



All of these, it may be remarked, are rare, or gradually dis- 

 appear in the farthest South-western counties of Devon and 

 Cornwall, and are totally wanting, with many others, in every 

 one of the smaller islands of the British group, excepting 16 

 and 17, that occur in Anglesey and Ireland, the Flora of which 

 last, its size considered, exhibits in an extreme degree the cha- 

 racter of a western and island vegetation, both in the paucity 

 and peculiarity of its indigenous species, and resembling in 

 these respects that of New Zealand, the Azores, and other 

 island groups lying remote from any large tracts of land or 

 continent. 



It is observable that Rhamnus catharticus, Bryonia dioica and 

 Campanula Trachelium, three species characteristic of the east- 

 ern and interior rather than of the western and coast Flora of 



* Every one tnows the diflBculty attending the cultivation and preservation 

 of the terrestrial Orchidaceae, and how little gregarious is the greater number 

 of the tribe. This holds true of Hahenaria viridis, which, seldom plentiful at 

 any time on a given station, is in this island so reduced in frequency that I have 

 seen but three, and those collected by others, in more than thrice as many years, 

 during which time I have not once fallen in with a specimen on any of my 

 innumerable herborizing walks within the limits of this Flora. 



