SPOROGONIUM OF LIVERWORTS 



283 



the apex ruptures irregularl)'. Owing to their unequal thick- 

 ening, the elaters tend to coil and bend as the contents of the 

 capsule become drier. This movement is, however, prevented 

 until rupture of the capsule takes place, when the tensions set 



Fig. 155. — The sporo,5onium of Pcllia. A, Small part of a thallus, showing 

 a mature sporogonium, with the ruptured calyptra (c.) at the base 

 (after Leunis). B, Longitudinal section through an almost mature 

 sporogonium, still enclosed within the calyptra (c.) ; the elaters are 

 shown as dark lines among the much larger spores. ca., wall of 

 capsule ; /., foot ; ;'., involucre : ».. neck of archegonium ; ;-.. rhizoid ; 

 s., seta; sp., spore. C, A group of spores (s/>.) and elaters (e.). 



up in the elaters are manifested in a wriggling movement which 

 loosens the mass of spores and flicks them into the air. Not 

 uncommonly tufts of elaters remain adhering to the top of the 

 stalk [e.g. Pcllia) or to the valves (Fig. 147, C). 



