FERTILIZATION 



65 



The young sporophyte grows down at first into the tissues 

 of the gametophyte, but finally it begins to elongate. The 

 lower part becomes stem-like and forms the seta, while the 

 upper part becomes enlarged. This enlarged portion becomes 

 differentiated into a calyptra and a capsule. 



The Calyptra is the loosely attached outer protective cover- 

 ing of the capsule. 



FIG. 31. Musci. Left, colonies of an theridia -bearing plants, right, colonies 

 of archegonia-bearing plants. 



The Capsule is differentiated into operculum, epiphragm, 

 peristome and spore-bearing tissue. 



The operculum is the lid which usually covers the upper 

 part of the capsule and separates circumscissilly when the 

 spores mature. 



The epiphragm is a network of fibrous cells covering the 

 spore-bearing tissue. The whole structure is circular in 

 outline and the cells are far enough apart to permit the pas- 

 sage of the spores. 

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