110 



Elementary Biology. 



FIG. 4\.Polytrichum piliforme. 

 (Lantzius- Beninga.) 



deep brown in colour. This 

 fringe of hairs forms the 

 peristomium. The hairs 

 are broad at their bases 

 and taper inwards, where 

 they are attached to a thin 

 plate or epiphragm, which 

 forms a temporary lid to 

 the theca after the removal 

 of the operculum. 



When the spores are 

 ripe the operculum is 

 forced off by the expansion 

 of the peristomium, and 

 the spores are shaken out 

 by the swaying of the long 

 seta in the wind. Each 

 spore is a cell covered by 

 an outer brown cell-wall or 

 exosporium and an inner 

 colourless cell- wall or en- 

 dosporium, and contains 

 protoplasm, oil globules, 

 and chlorophyll. The time 

 required for the develop- 

 ment of the asexual para- 

 sitic generation varies in 

 different species, but an 

 average period is three or 

 four months. The spore 

 germinates rapidly when 

 sown on moist soil, and 

 forms a protonema. The 



A, longitudinal section of theca. B, transverse general character of the 

 section : ?*/, wall of theca ; c//, operculum ; , , , 



c,c, columella ; p, peristomium; c p, epi- prOtOnema has already 



E^tf*3i^*S32i'4beai described (p. 104). 



peristomium. 



