336 FERNS : BRITISH AND FOREIGN. 



distinct from those of the present era. Not so the 

 Ferns,, for their beautiful and well-preserved remains 

 show that their fronds were of various sizes and forms, 

 in every way analogous to the present race ; having 

 free and anastomosing venation, round and linear 

 fructification, and, in some instances, almost identical 

 with species now living. At present, Ferns rank 

 amongst the widest spread of all the orders of the 

 vegetable kingdom, being found in more or less 

 number in all climates, between the most northern and 

 southern limits of vegetable life, and at elevations 

 ranging from the sea-level to 14-15,000 feet within the 

 tropics, their number in any localities being generally 

 in proportion to the degree of atmospheric moisture in 

 conjunction with elevation, the latter applying specially 

 to the interior of continents. Comparatively few 

 species are found in open, grassy, thinly-wooded 

 countries, whether it be the plain or mountain-slope ; 

 such districts are often in full possession of the most 

 gregarious and abundant of all Ferns, the common 

 Brake (Pteris aquilina), which, under slightly different 

 forms, and in some countries accompanied by different 

 species of Gleichenia, occupy vast tracts of the earth's 

 surface. In hot and moist plains, in valleys of great 

 extent, the number of different species are few ; even 

 in the valley of the Amazon, teeming as it does with 

 vegetable life, the number of Ferns found by Dr. 

 Spruce after he left the coast Flora, at Para, in his 

 journey of 2,000 miles, were very few. They became 

 more numerous on attaining an elevation of 1,500 

 feet, and in one locality, at a higher elevation, he 

 found 250 species in a diameter of fifty miles. 

 Another extensive tract with but few Ferns is the 



