TRUE MOSSES (BRYALES) 417 
growing out so as to form leaves, then a leafy sporophyte like 
those of Pteridophytes would be formed. In the third place 
there is a meristematic group of cells at the base of the sporophyte 
by which growth and production of spores are maintained for a 
period of time. 
Mosses 
General Description. — In general, Mosses do not need so much 
moisture as Liverworts do, and are, therefore, more generally 
distributed. They are common in moist places and some inhabit 
bogs and streams, but Mosses are also very common in dry 
places. They live on tree trunks, logs, stumps, rocks, soil, and in 
bogs and fresh water. In fact one can find Mosses nearly every- 
where. They often mass together in clumps and cushion-like 
masses which hold water much like a sponge. Many Mosses, 
especially those growing in dry places, can become dried out and 
then revive when they become moist again. The Mosses as a 
group have better differentiated gametophytes and sporophytes 
than the Liverworts. 
The Mosses are divided into three groups, Sphagnales, Andrea- 
les, and Bryales. The Sphagnales are the Sphagnums, which live 
in bogs where the accumulation of their plant bodies forms peat. 
The Andreales are a very small group of siliceous rock Mosses 
which will receive no further discussion, although they are inter- 
esting because they present a combination of characters which 
relate them to the Sphagnales, Bryales, and also to Liverworts. 
The group containing the vast assemblage of our most familiar 
Mosses is the Bryales. The Bryales, known also as the True 
Mosses, are the most highly organized of the Mosses. 
True Mosses (Bryales). — The most conspicuous part of the 
Moss plant is the gametophyte, which looks like Figure 372. It 
consists of a leafy stem attached to the substratum by rhizoids. 
In some Mosses the leafy stem is prostrate, but in many it grows 
erect. The leaves of the Moss plant, like the leaves of the foliose 
Liverworts, are quite simple. In most part they are only one 
cell in thickness. They have no stomata and no palisade or 
spongy tissues. Although they are called leaves, it is obvious 
that they are not like the leaves of the higher plants. But their 
cells contain chloroplasts and they make carbohydrates just as 
the leaves of the higher plants do. Stomata, palisade, and 
