I4 THE UNCOILING FRONDS. 



coal measures. The presence of great beds of coal in 

 lands that are now covered with ice and snow for a large 

 part of each year, indicate that they once supported a 

 luxuriant fern-flora. The temperature was then, of 

 course, much higher. The tree ferns' descendants still 

 retain their love for warmth, shade and moisture, and 

 perhaps are still as abundant upon tropical islands as 

 ever, but there is scarcely a spot on the globe without 

 one or more species, unless it is an absolute desert. 



Nearly all ferns are perennial, although individual 

 fronds seldom live more than a year. Many, even in a 

 climate like that of Canada, are evergreen. The tree- 

 fern with an erect trunk and a tuft of fronds at the sum- 

 mit is probably the typical form. Our common species 

 are supposed to be without trunks because they do not 

 rise above the earth but one has only to dig up the 

 nearest species to find that if it has not a true trunk, it 

 has what is equivalent to one. This is usually a hori- 

 zontal axis, bearing the crown of fronds at one end and 

 giving off roots especially from the under surface. It is 

 occasionally found upon the surface and seldom very far 

 beneath it. In some the axis branches and in most the 

 growing tip is advanced some distance each season, just 

 as the crown of the tree-fern is lifted higher in air. The 

 conditions under which our species exist, especially in 

 winter, are not favourable to the formation of aerial trunks 

 and they have therefore been modified for a life under 

 ground. 



Ferns bear no flowers, although one species is by 

 courtesy called the flowering fern and " fern-seed " is 

 still as elusive and uncertain a thing as it was in the time 

 of the Ancients. Many absurd ideas were entertained 

 regarding it, some of which are mentioned in the chap- 



