THE BRYOPHYTA: HEPATICAE, THE LIVERWORTS 407 



internal water tension set up as the elaters dry. This causes twisting, which 

 is violently released when the water tension breaks down, causing the elater 

 to spring back explosively into its normal form, thus scattering the spores. 

 On reaching the ground the spores germinate immediately to produce a tmy 



Lobe with 

 rhizoids 



Involucre 



Archegonia 



Fig. 389. — Morchantia polymorpha. Horizontal section 

 through archegoniophore, showing rhizoid channels in 

 lobes and involucres containing groups of archegonia. 



Seta 



Capsule 



Calyptra 





Fig. 390. — Marclnmtia polymorphs. Young sporo- 

 gonium showing de\elopment of spores and elaters 

 from archesporium. 



