ON THE PRESENT STATE OF OUR KNOWLEDGE OF 

 THE GEOGRAPHY OF BRITISH PLANTS. 

 (Concluded.) 



By J. Gilbert Baker, F.R.S., &c„ 



[The Annual Addkess of the President to the Membees or the Yorkshire 

 Naturalists' Union, at Selby, on March 3rd, 1^83.] 



Another important set of facts bearing upon the pedigree of our 

 indigenous plants, is furnished by their distribution beyond the bounds 

 of the island. Some of the common plants of the north temperate zone 

 have an extremely wide dispersion. Let us take a few of our best 

 known ferns as instances. O&munda regalis is spread in the old world 

 from Sweden to Japan, and reappears in the Himalayas, the Alps, 

 and the mountains of the Indian peninsula. In Africa it is found in 

 the Barbary States, Abyssinia, Cape Colony, Angola, and Sierra Leone ; 

 and in America it is spread from Canada and the Red River as far 

 south as Rio Janeiro. Cystopteris fragilis is found everywhere in 

 Europe and Asia, from Iceland eastward to Kamschatka, and from the 

 Arctic Circle southward to the Himalayas, where it reaches an altitude 

 of 15,000 feet. It reappears in the mountains of Abyssinia, Fernando 

 Po, Bourbon and Cape Colony, in Tasmania, New Zealand, and the 

 Sandwich Islands, and in America is found in the temperate regions 

 both on the north and south of the equator, and in many places in the 

 tropical zone amongst the Andes. Aspidium acuhotum, Nephrodium 

 filix-mas, and Pteris aqitilina are spread equally widely. Of the 1425 

 British species only about 300 are restricted to Europe, whilst 450 

 reach America, 250 the Himalayas, and nearly 100 the southern 

 hemisphere. We always take for granted that a species has spread 

 from a single centre, and if this be the case, what an enormous amount 

 of time we must allow for this wide diffusion of types to have taken 

 place, and what an amount of change in the configuration of sea and 

 land must have taken place since they first started upon their travels ! 



Another important field for investigation is the light thrown upon 

 the pedigree of species by the study of our more variable specific types. 

 I can see no solution that will in any way account for a wide mass of 

 facts except the Darwinian one — that between slight individual modifi- 

 cations, varieties, and sub-species and species, no clear line of demar- 

 cation can be drawn. Every fresh year teaches us that, even amongst 

 organisms v»^hich have been studied as closely as our British flowering 



plants, specific types that have been supposed to be stable and uniform 

 N.S., Vol. viii. May, 1883. 



