

I 



III. J. G. 1UKER ON THE GEOGRAPHICAL DISTRIBUTION OF FERNS. 



timnt but restricted to mountainous tracts, say 12; and, 3rd, species preeminently 



icted to the vicinity of the Mediter 



and Atlantic, say 18. 



1! 



leaves fifteen species 



one of which, Asplenium crenatum, is specially 



the other fourteen are scattered, more or less sparingly 



Centra] Europe, not a single one being preeminently eastern or having its head quarters 



a little within European bounds. The only widely (Utilised 



in .Win 



a 



coming 



Central- Europ.n ii species which we do not possess in Britain are, with some doubt as to 



the last, Onoclea germcdica, Cystopteris alp 



Asplenium ji 



d JBotrych 



mtaceum. On the other hand, eight of the south-western species enter into the British 



one of them, II>i,nenophyllum Tunbridgense, being widely dispersed, but two not 



list, . m m 



reaching further north than the Channel Islands 



Twelve species 



grow in the West 



African [alands which are not Europ 



*I)ioksonia Cidcita. 



Adiantnm renifarme. 



*Cheilanthes pulehclla. 

 Asplenium raonanthemum. 

 t'urcatum. 



These 



umbrosum. 



"*Aspidium falcinellum . 

 frondosum. 



Nephrodium molle. 

 *Poly podium drepanum. 

 Gymnogramma Totta. 

 Acrostichum squamosum 



The torn- marked with an asterisk are quite peculiar to these islands, the Dicksonia being 

 much the most distinctly marked specific type which this second district yields. Of the 

 other-, the A Hantum is Mauritian (but the Mauritian plant is a well-marked variety), 

 and Aapidium fro Iosi>m, long supposed to be peculiar, has been detected recently in 



Natal 



The other six are all widely diffused tropical and subtropical species, all being 

 met with in tropical Africa, so that in the fern-flora of these islands we cannot find any 

 trace of an American affinity. The number of Canarian species is 31, of Azorean 25. 

 The species common to the islands and Europe are all of the south-western or general 



Eur 



type, the 12 montane Europ 



species 



being 



entirely absent 



To the 



European list we get only two species added in North Africa, Nephrodium unitum and 

 Actiniopteris radiata—a very significant fact in illustration of the connexion between 



climat and fern-geography, as we shall see best when we come to contrast this addition 

 of only two species for an area of between two and three millions of square miles of sub- 

 tropical country, with the large number of species which are added in subtropical Asia 

 to those that grow further north. Both of these are widely dispersed tropical species. 

 1 he number of species peculiar to continental Europe is only six— Asplenium germanicum, 

 Hevjeri, Petrarch at, jissum, and Seelosii, and Cheilanthes hispanica ; Nephrodium cemulim 



confined to Britain, the Canaries, and Madeii 



D 



to the West 



African islands and Spanish penins 



of species not quite, but nearly peculiar to 



this second district, Nephrodium montanum extends only into Lapland and Geor 

 Asplenitnn, Ucmiouitis to the Cape Verde Islands. 



and 



3. Temperate Asia 



It is here, as compared with all the other temperate districts 



This district yields 413 species 



that the fern-flora reaches its maximum development 



18 per cent, of the total number, more than half the whole number of species that w 



inywhcre m temperate regions, twice as many as grow in any other temperate district 



