308 



THE PERISTOME OF THE CAPSULE 



The entire surface of the capsule is protected by a well-developed 

 epidermis but at the top a lid or operculum is cut off by a ring 

 of rather delicate mucilage-bearing cells, the annulus, which 

 swells at maturity and so assists in casting off the operculum 

 (Fig. 210, 3, r). Below the operculum a layer of cells, known 

 as the peristome, extends across the capsule and becomes greatly 

 thickened on its outer and usually on its inner walls. This layer 

 of cells is firmly attached to the walls of the capsule by rather 

 short thick-walled cells (Figs. 210, 3, p; 211, 6-8, p). When 

 the spores are mature, the more delicate cells break down, leaving 

 little more than a loose mass of spores and the peristome within 

 the capsule. The cells of the peristome break apart into teeth- 



FIG. 212. Germination of the spore: 3, early stage in the germination, 

 4, character of the branching, alga-like filaments that are finally developed 

 from the spore r, rhizoids which penetrate the ground; b, bud which will 

 develop into a leafy moss plant. 



like segments (Figs. 211, 7) and being very hygroscopic, co- 

 operate with the contracting capsule in forcing off the operculum. 

 After the removal of the operculum the mouth of the capsule is 

 covered by the peristome which now appears as a fringe of teeth 

 radiating out from the walls of the capsule (Fig. 210, 4). The 

 teeth of the peristome are always in multiples of two and form 

 one or more, usually two layers, accordingly as only the outer or 



