CHAPTER XV 



LIFE HISTORY OF A MOSS 



176. Variety of Mosses. — There have been described and 

 named over 12,000 different species of Musci, or mosses. 

 Obviously, in an introductory study, we can only get a 

 glimpse of so large a group. A comparative study of the 

 species has led to the recognition of three distinct orders 

 as follows: 



Musci 



1. Sphagnales (the peat-mosses) 



2. Andreseales (the black mosses) 



3. Bryales (the true mosses) 



Of these the Sphagnales are considered the most primitive, 

 and the Bryales most highly developed. The Sphagnales 

 will be considered first. 



177. Habitat of Sphagnmn.— Peat-mosses, as the name 

 impHes, grow in swamps and lake margins, usually in 

 dense clumps or thick mats, in places forming the familiar 

 peat-bogs of northern regions. They are usually of a very 

 pale green color, often almost white, especially just 

 below the top, and frequently with a tinge of red or 

 yellow. 



178. Description of Sphagnxim. — The plant consists of 

 an upright central axis or stem, with a central, pith-Kke 

 portion of thin-walled parenchyma (Fig. 139.) The cell- 

 walls of the outer portion, or cortex, are thicker and often 

 tinted with a reddish pigment. The cortex varies in thick- 



13 193 



