BRYOPHYTA—HEPATIC^ 



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 808). 



The elongation of the stalk is proceeding while the arche- 



Fig. 866. Thallus of Marchantia with gemmffi cups, &, and antheridiophore, d. 

 The upper figure Is a section through part of d. a,b, c, d, e, f. Autheridia 

 in depressions in successive stages of development. After Kny. 



gonia are being developed, and they 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 

 frpHi it, called the perichcetium, which often surrounds a group 



