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



recorded species to an extent which no one who has not made Perns a special study is 

 likely to anticipate. The great difficulty in botanical geography in comparing lists of 

 species of one group or of one country with those of others is, that species are limited by 

 different authors upon such widely different principles. The extent of this divergence 



jst Ferns will be shown most clearly by a few figures. Where De Vriese has 94 

 Marattiaceaa, we have only been able to define 9 ; where Van den Bosch has 450 Hymeno- 

 phyllacea?, we have 149 ; where Presl has 21 species of Osmunda, we have 5 ; where 

 Tee has 17 species of Lomariopsis, we can only define 1 ; where Sturm has 12 Brazilian 

 species of Lygodium, we have only 2. The total number of species, in the Synopsis- 

 sense of the term, which we have been able to make out is a little over 2200 ; but I am 

 certainly within the mark in saying that if all the tribes were uniformly worked out 

 upon the plan followed by all or any of the authors whose names have been quoted, we 

 should have five or six thousand. All experience goes to show that if for botanico- 

 geographical purposes we do not confine our numerical comparisons to well-marked 

 species, we soon become entangled in a maze of confusion. The number of species 

 which we have been able clearly to make out and define, of which there are not specimens 

 in the Kew collection, is very small ; and in the same way, in the following Table II. and 

 the remarks founded upon it, in very few cases are they registered for districts without 

 specimens having been actually examined. The districts adopted are as follows, viz. : 



1. The Arctic zone all round the world. 



2. The rest of Europe and the extra-tropical part of Northern Africa, including the 

 extra-tropical western islands. Species peculiar to these latter are marked C. 



3. Temperate Asia. All the species in the third column marked with the figure 3 

 inhabit the temperate region of the Himalayas ; but those marked S are confined to the 

 subtropical zone on the southern flank of the Himalayan range. The few species peculiar 

 to Western Asia are marked W ; those peculiar to the rest of the continent outside the 

 Himalayas are marked C, and those peculiar to Japan are marked J. 



4. Temperate North America, not including any part of Mexico. 



5. Extra-tropical South Africa, including the island of Tristan d'Acunha, the species 

 peculiar to which, so far as this district is concerned, are marked T. 



6. New Zealand, Van Diemen's Land, and temperate Australia, including the small 

 south temperate islands. Species peculiar to the latter are marked N ; those peculiar to 

 Australia, with Van Diemen's Land, A ; and those peculiar to New Zealand, Z. 



7. Temperate South America. 



8. Tropical Africa. Species peculiar to the eastern group of islands (Madagascar, 

 Mauritius, Bourbon, and the Comoro Isles) marked M ; to the Seychelles, marked S ; to 

 to the east side of the continent, marked E ; to the west side of the continent, marked 

 W ; to St. Helena, H ; and to Ascension Island, A. 



* 9 



9. Tropical Asia, including the Malayan and tropical Polynesian islands. Species 

 peculiar to the latter, marked M and P respectively, and species peculiar to Ceylon and 

 peninsular Hindostan, marked H. Formosa, Hong Kong, tropical China, and the 

 Philippines, and the Malay peninsula, are included under M. Species peculiar to Tro- 

 pical Australia marked A. 







