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: 



[ I. Sphagnales (the peat-mosses) 

 Musci 2. Andreasales (the black mosses) 

 1 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 Sphagnum. — Peat-mosses, as the name 

 implies, 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 Sphagnum. — The plant consists of 

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

 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- 



? 193 



