DISTRIBUTION IN TIME AND SPACE. 67 



COSMOPOLITAN SPECIES. 



Polypodium vulgare. 

 Pteris aquilina. 

 Asplenium trichomanes. 



filix-foemina. 

 Cystopteris fragilis. 



Ophiogkesum vulgatum. 

 Botrychium Virginianum. 



ternatum. 

 Equisetum arvense. 



hiemale. 



Selaginella rupestris. 

 Azolla Caroliniana. 



1 43. Local Lists. The number of species found in a sin- 

 gle locality is usually limited, yet in certain favored locations 

 there is a marked diversity. As an instance, in one of the 

 habitats of the rare hart's-tongue * the writer has collected 

 twenty-seven species illustrating fourteen genera within the 

 radius of a thousand feet. Such localities, however, are com- 

 paratively rare, and must include wide diversity of soil and 

 shade within very narrow limits. 



Onondaga County, New York, possesses perhaps as many 

 ferns as any county in the entire country, including 41 species. 

 32 are catalogued from Essex County, Massachusetts. Several 

 State lists more or less complete have been compiled, and are 

 noticed in the literature below. Carefully prepared lists from 

 all the States and Territories would be a valuable addition 

 to our knowledge of geographic distribution. 



144. Geologic Distribution. It is well known that the 

 plants and animals now existing on the earth are not the same 

 in kind as those of former ages. Geologists have carefully 

 studied the stony heart of nature, and have drawn therefrom 

 the story of the development of land and sea, and the succes- 

 sive populations that from time to time have held possession 

 of our globe. Plants furnishing the natural food for animals 

 must have preceded animal life, yet in the earliest geologic 

 ages the remains of animals are far more numerous. The 

 abundance of the deposits of graphite and iron-ore in the earli- 

 est or Archaean rocks indicates the existence of extensive plant 

 growth, but the remains are so transformed as to mak2 it im- 

 possible to determine the character of this primeval vegetation. 



1 45. In the succeeding Silurian age the fossil remains in- 

 dicate the existence of algae or sea-weeds in abundance, and a 



* " Green Pond," one mile east of Jaraesville, Onondaga County, New 

 York. 



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