MOSSES AND LIVERWORTS. 



257 



and Hypnum the capsule has when young a soHd core. 

 The spore-forming layer surrounds this central part and 

 is separated from the outside wall by a very loose 

 tissue containing many air-spaces which will provide 

 the developing spores with oxygen. The capsule opens 



Fit;. 32 —Mosses, (i) Leaf of Rhacomitrirm. (2) Peristome teeth of Campy- 

 lopus ; several have been broken off for the sake of clearness. (3) Hood or 

 Calyptra (archegoniiim wall) of Encalypta. (4) 1 uft of earth formed by a species 

 of Bryum to show the interlacing of rhizoids (the stems are very much closer 

 together in nature). (5) Lid or operculum of Campylopus capsule. 



at the top only. There are three coverings. Two of 

 these protect the capsule when young and are thrown 

 off when it is ripe. These are ( i ) the " calyptra;' a sort 

 of hood and often covered with hairs, which is the upper 

 part of the archegonium, and (2) the " operculum^' a lid 

 which fits on to the top of the capsule. The third 



(B7) R 



