SPOROGONIA 355 



1. The. clearly marked apophysis. 



2. The presence of two concentric air-spaces, 

 with the spore-sac between them. 



3. The more bulky operculum. 



4. The proportionately smaller peristome, consisting 

 in this case of a series of curved cells, with thickened 

 lateral walls : their tips are connected with 



5. The epiphragm, which remains as a transverse 

 membrane after the thin-walled tissue above and below 

 it has dried up in the course of ripening of the 

 sporogonium. 



6. The less clearly marked annulus. 



From these examples it appears that the peristome may 

 be differently constructed in various mosses : it may be added 

 that in Splachnum the teeth of the peristome are not, as in 

 Funaria, tatters of cell-wall, but are composed of rows of cells. 

 In order to understand the function of the peristome, where it 

 consists, as in Fwiaria, of a fringe of tatters, take a mature sporo- 

 gonium, gently remove the operculum, and examine it under a 

 low power upon a slide, breathing upon it occasionally : the teeth 

 of the peristome will be seen to execute movements, which appear 

 as a succession of jerks, owing to the rough edges of the peristome 

 catching upon one another : the spores, which appear to be forced 

 upwards by the drying and contraction of the tissues, may thus 

 be nicked away to a considerable distance from the mouth of the 

 sporogonium. 



In Polytrwhum the peristome does not act in this way : at 

 the period of ripeness the capsule becomes inverted owing to 

 curvature of the apex of the seta, and the spores are dusted out : 

 these points should be observed, as also similar ones relating to 

 other Mosses. 



XVII. Scatter spores from the ripe sporogonium of 

 Funaria or Polytrwhum over moist soil, and keep them 

 at a moderately high temperature, under a bell-glass, 



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