but with New Jersey, smaller than single counties of California, 

 and with a comparatively homogeneous surface and climate, but 

 which includes in its flora 39 ferns and 27 other fernworts — but 

 10 less than are found in this great State. 



It appears, therefore, that the conditions in California do not 

 conduce to the development of an extensive fern flora. The 

 ferns are a tropical family, and flourish best where a moist at- 

 mosphere is combined with an equitable warmth. The at- 

 mosphere of the northern coast is sufficiently moist, but the tem- 

 perature is low. As a result there is a great abundance and a 

 luxuriant growth of ferns, but they are confined to a few species, 

 mainly, indeed to a single one, the cosmopolitan bracken. 



The atmospheric aridity elsewhere is too great, and only 

 xerophytic ferns can exist, save for a few species which are 

 closely confined to the immediate vicinity of water. The numer- 

 ical abundance of individuals, as well as the multiplication of 

 species, is of those ferns which, by the minute subdivision of 

 their leaves, by their habits of vegetating, by the possession of 

 hairy, scaly or powdery induments, usually by the union of 

 more than one of these devices, are able to flourish with scanty 

 and irregular supplies of water. Accordingly Pcllaca, Notholaena 

 and Chcilanthes are the genera which have the greatest develop- 

 ment. 



Space does not permit an extended discussion of the dis- 

 tribution of the fern flora. It is determined by the action of the 

 same causes which have disposed the general flora of the 

 State. Disregarding minor modifications, the essential considera- 

 tion is the interrelation of the two great life-currents which 

 here meet and interpenetrate. From the north comes a number 

 of boreal ferns, some of them barely passing across the boundary, 

 others following for certain distances down the coast ; while the 

 most important line of descent is along the high altitudes of the 

 Sierra Nevada. By this route such a northern plant as Crypto- 

 grammc acrostichoides nearly attains the southern boundary, 

 and Woodsia Orcgana passes over it into Lower California and 

 Arizona. 



On the opposite hand, from the southeast come ferns of the 

 Sonoran type, most abundant in the south, but in some cases 

 passing well to the north, as is instanced by Gymno gramme trian- 

 gularis, which reaches British Columbia. It is mainly in this 



