20 THE POLYPOD FERN. 



leaves, while the Moulds, Mushrooms and Lichens have 



neither. Not less than 2000 species have been described, 



chiefly inhabiting the cool and rocky regions of the Earth. 



On the cinders of Mt. Hood they form the first verdant 



specks of vegetation, and the cliffs of Mt. Washington are 



already green with mossy tufts and beds. Cold swamps are 



everywhere being filled with Sphagnum and other Mosses, 



whose remains accumulate and are, in time, condensed to 



peat — a valuable fuel in some countries where wood and 



coal are scarce. 



Review of the Scientific Terms used in this lesson : Cilia. 

 Dicliotomous. Fugacious. Subulate. Species. 



III. THE POLYPOD FERN. 



Description. — This comely Fern is found everywhere in 

 old forests, growing on stony steeps, and covering the rocks 

 and boulders with a matted turf composed of their tangled 

 stems and roots. 



Analysis. — We may conveniently divide this plant into 

 two portions or regions ; first, that of the stem and root 

 under ground (subterranean); second, that of the leaf and 

 fruit above ground (aerial). The analysis will then proceed 

 as before. 



Tlie ^ool consists of a numl)er of thread-like or hair- 

 like fibers, branching into tinj fihrils, growing all along the 

 stem. 



The Ste?n creeps about in the soil. It is many-branched, 

 and covered with soft, narrow scales. As it never rises into 

 the air it is properly a root-stock or rliizome. * 



* Plants with rhizomes are not uncommon. They are always perennial, i. e., living 

 from year to year, and otherwise noted for their strong vitality. Those which have 

 rhizomes long, slender, branching, are inclined to take exclusive possession of the 

 soil, and so become in fields and gai'dens troublesome weeds. Such is the Polypod 

 in Europe. On the contrary, in sandy sea-shores and dykes they are useful, binding 

 r-he soil into a firm turf resisting the washing of the waves. See XJU and LXV. 



