

MR. J. G. BAKER ON THE GEOGRAPHICAL DISTRIBUTION OF FERNS. 



The g, at Plan of Distt 



— To illustrate the most striking point about the 





uci 1 distribution of 



Order, I will b 



a 



quotat 



from Mr. Dai 



8 te few families, many subfamilies, very many genera, and a still greater number of 



of 



-> 



confined to a single region ; and it has been observed by 



naturalists that the most natural 



those genera in which the species are most 



( 



ly allied to one another, are generally. local, or confined 



The remark 



point about the distribution of Feins is, that, as may be seen from this last Table 



their is so little trace amongst them of this concentration of allied forms in the same 

 district Most of the tribes are distributed through the districts in very much the same 

 proportion as the whole Order; and in the genera there is no striking exception to the 



imc plan. 



only instances in which any district has 

 following : — 



Vlthough three-quarters of the species are confined to single districts, the 



more than half the species of a tribe are the 



Tropical A 



Cyathese, Acrostichesc, Schizasacece, Marattiacese 



Tropical Asia. — Davallicae, Lindsayese, Ophioglo 



A 



Ophioglossacese 



That is to say, in eight instances out of 180 possible cases; and the highest percenta 



which anv tribe 



more than 100 species attains in any district 



Con 



[uently th< leading characteristic of each district is expressed by giving the pei 

 of the whole number of species which it yields,— not, as is so often the case in fl 



plants, by Baying that such and such orders, groups 



n 



V 



r 



characterize it special!) 



The theoretic bearin-s of this, which it is beyond the scope of my present paper to 



o 



discuss, are well worthy of attention 



Origin of Species, p. 353. 



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