two equally developed 
parts. The archegonia. 
(Fig. 899) and the 
antheridia (Fig. 400) 
are borne in a groove 
which extends longi- 
tudinally through the 
center of the upper 
part of the thallus 
(Figs. 397, 898). The 
fertilized egg develops 
inside of the arche- 
gonium. It gives rise 
to a single rounded 
sporangium without a 
stalk (Fig.401). This 
sporangium consists 
of an outer layer of 
sterile cells and nu- 
BRYOPHYTA 

Sh sae B 
ee 
Fic. 405. Section of a portion of a thallus of 
Marchantia 
Below, colorless tissue ; above, air chambers with 
photosynthetic cells. Note the stomalike open- 
ing into the central chamber and the large cells 
which form the side walls of the chambers. (x 200) 
merous spores. The sporangium wall is an evanescent structure 
which almost entirely disappears before the spores are mature, 

Ss 
| Fia. 406. Marchantia 
Left, female plant with specialized branches which bear archegonia on their un- 
der surfaces; right, male plant with specialized branches which bear antheridia 
sunken in the upper surface. (xX 13) 
