518 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



581. " Owing to the sharply contrasted seasons of temperate 

 continental North America, there are even fewer ferns in that 

 vast tract of country than there are in Central Europe : only 

 fifty species are mentioned in Hooker's Flora Boreali-Ame- 

 ricana, and as many in Gray's Flora of the North United 

 States ; whereas Britain alone contains thirty-six. 



582. " Advancing eastward, we find that the European Flora 

 contains only sixty species ; and in the Flora of the whole 

 Russian dominions, extending from the Baltic to the Pacific, 

 and from lat. 40° to the Arctic circle, scarcely as many are 

 found. 



583. " Of the number of ferns indigenous to the tropics no 

 accurate estimate has yet been published ; but we know that 

 nearly three hundred species have been collected in the Philip- 

 pine Islands, and that there are perhaps two hundred in Java, 

 and about as many in British East India. 



584. " In the south temperate zone New Zealand presents by 

 far the richest assemblage of ferns, nearly one hundred and 

 twenty species, besides many well-marked varieties, occurring 

 in its islands ; and of these eight are tree ferns, and several 

 others sub-arboreous. In the dreary islands of the Antarctic 

 Ocean ferns still predominate ; twenty-one species inhabit 

 Fuegia and the Falkland Islands ; one forms matted tufts on 

 the sterile soil of Kerguelen's Land (where only sixteen 

 flowing plants have been found) ; and about as many inhabit 

 Lord Auckland's and Campbell's Islands to the south of New 

 Zealand. 



585. " Of the extended distribution of the species, a few exam- 

 ples must sufiice : thus Oystopteris fragilis has been met with 

 in the temperate and colder humid regions of both hemispheres 

 in the Old and New World, extending from the Arctic circle to 

 the mountains of Tasmania. Gym^wgramma leptophylla has a 

 scarcely less extensive range, and is found in warmer latitudes ; 

 whilst Pteris aquilina is found in almost all temperate and 

 sub-tropical countries, under, however, many different names. 

 Of the fifty N. United States ferns, fifteen are also British, 

 and fully one half of the British species are also found in the 

 Himalaya mountains. Comparing the Fern Flora of Britain 



