H. BOTANY AND HORTICULTURE. 373 



divisions. The first of these he calls the Cosmopolitan, which 

 embraces two species (Pteris aquilina and Asplenium tri- 

 chomanes), distributed over the globe in both temperate and 

 tropical regions. Pteris aquilina lives in sandy barrens, and 

 is found every where from Lapland in the North to New 

 Zealand and Tasmania in the South, in America reaching 

 from Labrador to Alaska and the Isthmus of Panama. 



Species of the second, or Boreal division, occupy the north- 

 ern part of the United States, extending through Canada and 

 British America, some of them to Labrador, Greenland, and 

 Alaska, and represented also in the northern sections of the 

 Old World. Of these there are twenty-seven species. 



In this group we find an illustration of what has been no- 

 ted by Professor Gray in regard to flowering plants, namely, 

 a much closer relation between the species of Western Amer- 

 ica and Eastern Asia than between those of Eastern America 

 and Western Europe. Thus the Asplenium septentrionale is 

 widely distributed in the mountains and colder portions of 

 Europe and Asia, but is only known in this country in the 

 Rocky Mountains as far south as latitude 32. 



Pellcea gracilis, an American form, occurs in the Old World 

 only in the Himalaya Mountains. 



Third, the Appalachian division. The species occupy the 

 mountainous and hilly regions east of the Mississippi, often 

 to the coast, and northward to Canada, in some few instances 

 occurring: also in the Old World. The number under this 

 head amounts to about thirty-eight. 



Fourth, the Pacific division, which contains species extend- 

 ing to the western borders of the continent, from Alaska to 

 California, in a few cases appearing also in the Rocky Mount- 

 ain region. Here we have seventeen species. 



Fifth, the New Mexican division. Of this some of the spe- 

 cies occur in Mexico, and even in South America ; a few also 

 in California. There are twenty-seven species enumerated 

 under this head. 



The sixth, or the Tropical division, includes twenty-two 

 species inhabiting the borders of the Gulf of Mexico, most 

 of them extending to the West Indies and tropical America. 

 Of these, one, Trichomanes petersii, is quite local, having 

 been found only in Alabama and Florida. 



Of 125 species enumerated, sixty-nine, or about fifty-five 



