n8 NATURAL HISTORY BULLETIN. 



reference-books, by Prof. L. H. Pammel who furnished 

 Hooker's /cones Filiciim, and by Dr. C. M. Hobby, who loaned 

 his line collection of Hawaiian Ferns for comparison. 



Tropical America is the Fern-paradise of the earth. No 

 other corresponding division of the earth's surface presents as 

 great a total number of species, or as many species which are 

 peculiar to it. Nowhere else is the great variation in form 

 and size, in structural characters and habits of growth, and 

 in the arrangement and character of the reproductive organs 

 better shown than here. This richness in the Fern-flora, 

 exhibited in almost unlimited variety, is no doubt accounted 

 for by the topography and contour of that part of the Amer- 

 ican continent which lies within the tropics. It is narrow 

 when compared with the continents of the Old World, and it 

 contains high mountain-chains which form its longest axis. 

 Its narrow form brings all of it more or less within the 

 influence of the adjacent oceans, which furnish to most of it 

 an abundance of moisture. Its high mountains supply all the 

 conditions effected by altitude, and moreover cut off the other- 

 wise abundant moisture from certain areas. We have thus 

 within comparatively restricted limits all the possible degrees 

 of moisture and temperature, and the effect of environment 

 finds abundant expression in the great variety of fern structures. 



Excepting Palms perhaps, Ferns form the most conspicuous 

 feature of the tropical vegetation. In size they vary from 

 tiny representatives of the genus Trichomanes measuring only 

 a fraction of an inch in height, to clinging vines like Blechnum 

 volubile single fronds of which often exceed thirty feet in 

 length, or to splendid tree-ferns which form the crowning 

 glory of tropical vegetation. 



Every conceivable form of outline and degree of division 

 greet the eye, and in texture some rival the filmiest lace, while 

 others develope thick leathery fronds wholly out of harmony 

 with our ordinary conception of Ferns. In habit the varia- 

 tion is fuHy as great. In western Nicaragua, for example, 

 where there is a distinct dry season, Ferns growing on bare 



