336 
FERNS : BEITISH AND FOREIGN. 
distinct from tliose of tlie present era. Hot so tlie 
Ferns, for tlieir beautiful and well-preserved remains 
sliow that tlieir 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 a quilina), which, under slightly different 
forms, and in some countries accompanied by different 
species of Gleiclienia, 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 
