20 THE P6LYPOD FE&ff. 



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. 

 Dichotomous. 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. 



The ffioot consists of a number of thread-like or hair- 

 like fibers, branching into tiny fibrils, growing all along the 

 stem. 



The Stem 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 rhizome.* 



* 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, hranching, are inclined to take exclusive possession of the 

 soil, and so hecome in fields and gardens troublesome weeds. Such is the Polypod 

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

 the soil into a firm turf resisting the washing of the waves. See XTTI and LXV. 



