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BOTANY: PRINCIPLES AND PROBLEMS 



the archegonium are carried up with it and form a protecting 

 cap or calypira which covers the young capsule. The capsule 

 itself (Fig. 197) possesses a central columella and much other 

 sterile tissue, so that the spore-bearing layer, which surrounds 

 the columella, is relatively thin. The operculum drops off at 



Fig. 197. — Longitudinial section through the capsule of a moss (Polytrichum). 

 st, seta, ap, spophysis. w, wall, c, columella, s, spore-sac, surrounded on 

 both sides by loose tissue. {From Goebel). 



maturity and the liberation of the spores is controlled by a ring 

 of teeth projecting inward from the edge of the wall. Just 

 below the capsule there is typically an enlarged region, the 

 apophysis, which is often brightly colored and may sometimes 

 possess chlorophyll. The capsule is very diverse in size, shape, 

 and structure throughout the whole group. 



