THE EARLY JULY FLOWERS. 201 
The ferns of the temperate regions vary in height 
from two or three inches to several feet, but some of 
the tropical species merit their name of tree-ferns by 
their height of twenty to twenty-five feet, vying with 
some of the palms in size and beauty. The ferns are 
among the first families of the land. They came early, 
and came to stay. Their fossils, “footprints on the 
sands of time,” are found in rocks from the Devonian 
Age downward. Coal shales abound with them, some- 
times many species being represented on one slab, as 
perfect as on the day when they were imprisoned. Ifa 
living fern could speak, it could hardly tell a plainer 
tale than these mute relics. 
With the naked eye, only the outer beauty of ferns 
may be seen. The round or elongated spots, brown or 
black, on the under surface of the frond often pass un- 
observed. These spots are called sorvz, and are made 
up of little cup-shaped bodies called thece. The thece 
are filled with spores, from which new plants are de- 
veloped. All these parts are so minute, except the 
sori, as to be invisible without the microscope, or at 
least not to show their true form. But under the com- 
pound microscope a whole new world of wonders is 
laid open. I shall not soon forget the first time that I 
placed a piece of mature frond of Aspidium marginale 
on the stage of a compound microscope with a two-thirds 
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