278 



STRUCTURE OF CAPSULE 



the annulus, which swell at maturity and so assist 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 



Fig. 210. The mature sporophyte of Polytrichum: 1, moss plant bearing 

 spbrophyte. \A, calyptra removed, showing capsule, which has curved to 

 one side. 2, capsule, the calyptra, 2.1. removed, showing the operculum or 

 lid and the enlarged apophysis, a, at hase. 2B, capsule with operculum 

 removed, showing the teeth-like peristome and the epiphragm, which has 

 been lifted up at one side. 3, section of nearly mature capsule — sp, cyl- 

 inder of spore-forming cells that is surrounded on its inner and outer 

 sides by loosely arranged chlorophyll cells ; 0, operculum ; r, annulus ; />. 

 peristome; e, epiphragm; a, apophysis. 3A, stoma of apophysis. 35, cross- 

 section of capsule — sp, spore-forming cells. 4A, portion of mouth of cap- 

 sule, showing position of peristome and epiphragm in dry weather. 4B, 

 peristome pressed down on epiphragm, closing the capsule in damp weather. 

 — H. O. Hanson. 



