MOSSES 



189 



Fig. 173.— Capsule of Polytrichum (15 times enlarged). 

 1. Capsule with hood (calyptra); 2. Capsule without it; L. 

 3. Lid fallen off; the wind sheds the spores. 



Lid. 



by spores. The Ferns, as we have seen, form the spores in 

 clusters of spore-cases, generally on the under-side of the leaf; 



the Mosses, however, throw up a 

 stalked, urn-shaped body from the 

 centre of the stem, in which the 

 spores are produced. This little 

 vessel is protected by a dry, fibrous 



hood (caly- 

 ptra), like 

 the thatch 

 of a hut 

 (fig. 173, 1) 

 When the 

 spores are 

 ripe, the 

 hood is 

 thrown off. 



The capsule, shut up by a small, pointed lid (2), now appears and 

 soon places itself 

 horizontally (a). 

 The lid eventual- 

 ly drops also and 

 discloses a pale- 

 grey membrane, 

 attached at its 

 margin to the 

 capsule by a 

 number of tiny 

 teeth (tig. 174). 

 These teeth are 

 very susceptible 

 to moisture. 

 When they get 

 wet, they bend, 

 and while bend- 

 ing press the membrane down, thereby completely shutting up 

 the capsule with the spores. When dry, they stretch themselves 



Fig. 174. — Upper face of capsule (50 times eularged). 

 When air dry: teeth loose, spores issuing between teeth 

 and membrane (H); 2. when damp: teeth tight, holes 

 shut up. 



