47 



THE CANADIAN NATURALIST. 



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central axis of the capsule, and named the Columella, the apex of 

 which joins the lid, and sometimes falls away with it, though 

 occasionally we see the columella projecting from the mouth of 

 the capsule like a style (figs. 21, 22). The lid having fallen 



Fig. 21. Section of upper part of fruit of Mnium hornum, a. wall of 

 capsule, b. annulus, c. lid, d. tooth of outer peristome, e. tooth of 

 inner peristome, /. cavity of sporangium and spores, g. Columella. 



away, the mouth of the capsule is seen, sometimes naked, when 

 it is termed gymnostomous, but usually adorned by the beautiful 

 appendage named the Peristome, consisting of curious hygroscopic 

 tooth-like processes in a single or double series. 



The simple peristome, or the outer one when double, originates 

 from the lining membrane of the capsule ; its teeth are always 

 constant in number, 4, 8, 16, 32, 64, and present an infinite variety 



Fig. 22. Part of inner and outer peristomes of same. 



