BRYOPHYTA— HEPATIC.E 



107 



what like the ribs of an umbrella. The archegonia are 

 developed on its under surface in the angles between the ribs 

 and the stalk {figs. 867 and 868). 



The elongation of the stalk is proceeding while the arche- 



FiG. 866. 



r/ 



Ficj. 860. Thallus of Marcliautia with geumut; cup.-, b, and antlieridiophore, d. 

 The upper figure is a section through part of d. a, h, c, d, e, f. Antlierirtia 

 in depressions in succeesive stages of development. After Kny. 



gonia are being developed, and thej' do not spread out freely- till 

 fertilisation is effected. 



The structure of the archegonia has been already described. 

 They are not embedded in the tissue of the receptacle as are 

 the antheridia, but they are invested by a peculiar outgrowth 

 from it, called i\\e liericlicetium, which often surrounds a group 



