CHAPTER XI 
DIVISION BRYOPHYTA 
The bryophytes are composed of two classes of plants, 
the Hepaticae (liverworts) and the Muscc (true mosses). ‘The 
bryophytes are small plants most of which grow in moist places, 
although some live in dry habitats and will revive after being 
dried. Bryophytes do not 
have roots but are anchored 
to the substratum by hair- 
like rhizoids. The mosses 
are differentiated into a cen- 
tral axis, or stem, and small, (= 
spirally arranged leaves (Fig. Dr 
418). Some of the liverworts 
are thallus plants (Fig. 397), 
while others have stems and 
delicate leaves (Fig. 413). | 
In those with stems and RX 
leaves there are two dorsal © | 
rows of leaves arranged along Fig. 397. Thallus of Riccia 
the sides of the stem, and The dark rounded bodies are mature sporo- 
. ; phytes which are embedded in the thallus, 
usually a third small row on while the lighter bodies are immature 
the ventral surface. The sporophytes. (x 2) 
leaves of most mosses have 
a midrib, while such a structure is not found in any of the 
liverworts. The female reproductive organ of the bryophytes 
is an archegonium (Fig. 399). This is a flask-shaped structure 
which, when mature, contains a single egg. Spermatozoids are 
borne in large numbers in antheridia (Fig.400). The development 
of the fertilized egg results in the production of a sporophyte, 
which, in most cases, consists of a sporangium, or capsule, a stalk, 
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