430 PHARMACEUTICAL BOTANY 
at maturity, throwing off the lid. The peristome teeth are very 
hygroscopic. During rainy weather or when the atmosphere is 
very humid they bend inward preventing the escape of the spores. 
During dry weather they straighten out and in this process lift 
_ out some of the spores and allow others to sift out from the cavity 
of the capsule. This completes the asexual or sporophyte 
generation. The spores falling to the damp soil germinate into 
protonemata, thus completing the life cycle in which is seen an 
alteration of generations, the two phases, gametophyte alternat-. 
ing with sporophyte. 
