THE GKEAT GROUPS OF BRYOPHYTES 



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Mosses, which are sometimes called the Bryum forms, to 

 distinguish them from the Sphagnum forms. They are 

 the representative Bryophytes, the only group vying with 

 them being the leafy 

 Liverworts, or Junger- ^ 

 mannia forms. They 

 grow in all conditions 

 of moisture, from actual 

 submergence in water to 

 dry rocks, and they also 

 form extensive peat de- 

 posits in bogs. 



The sporogonium has 

 a foot and usually a long 

 slender seta, but the cap- 

 sule is especially com- 

 plex. When the lid-like 

 operculum falls off, the capsule is left like an urn full of 

 spores, and at the mouth of the urn there is usually dis- 

 played a set of slender, often very beautiful teeth (Fig. 

 292), converging from the circumference toward the center, 

 and called the peristome, meaning "about the mouth." 

 These teeth by bending inward and outward help to dis- 

 charge the spores. 



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A W^ B 



Fio. 292. Sporogonia of Grimmia, from all of 

 which the operculum has fallen, displaying 

 the peristome teeth: A, position of the teeth 

 when dry ; B, position when moist. — After 

 Kerner. 



