CHAPTER XXIV 
TYPES OF CRYPTOGAMS; BRYOPHYTES 
305. The Group Bryophytes.— Under this head are 
classed the liverworts and the mosses. Both of these 
classes consist of plants a good deal more highly organized 
than the thallophytes. The most familiar liverworts and 
mosses are terrestrial, but some are true aquatics. Bryo- 
phytes have no true roots, but they have organs which 
perform the work of roots. Some of them have leaves 
(Fig. 167), while others have none. Fibro-vascular bun- 
dles are wanting. The physiological division of labor is 
carried pretty far among all the bryophytes. They have 
special apparatus for absorbing water and sometimes for 
conducting it through the stem; stomata are often present 
and sometimes highly developed. There are chlorophyll 
bodies, often arranged in cells extremely well situated for 
acting on the carbon dioxide gas which the plant absorbs, 
that is, arranged about rather large air chambers. 
Reproduction is of two kinds, sexual and asexual, and 
the organs by which it is carried on are complicated and 
highly organized. An alternation of generations occurs, 
chat is, the life history of any species embraces two forms: 
a sexual generation, which produces two Einds of cells that 
by their union give rise to a new plant; the aserwal gen- 
eration, which multiples freely by means of special cells 
known as spores. 
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