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. Andreaeales (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 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- 
is 193 
