THE MARCHANTIA GROUP 



283 



Fi<;. 250. Female plant of 

 Marehantia 



Showing the umbrella-like arche- 

 gonial receptacles in various 

 stages of development 



on stalked, umbrella-like 

 receptacles, which are 

 really much-modified 

 branches of the thallus. 

 They bear either anther- 

 idia or archegonia, and 

 the two sexual organs are 

 not found together on the 

 same plant. The anther- 

 idial receptacle (Fig. 249, 

 A) is shorter than the 

 archegonial, and the top 

 is a flattened disk with a 

 lobed or scalloped margin. 

 The antheridia (Figs. 243, 

 249, B] lie in cavities or 

 pits along radiating lines 



FIG. 251. The female receptacle of 

 Marehantia 



A, portion of a lengthwise section of a young 

 receptacle (semi-diagrammatic), showing a 

 row of archegonia hanging down from the 

 lower surface, the youngest being nearest the 

 stalk : air chambers are present on the upper 

 surface; I, one of the finger-like lobes back of 

 the section, the diamond-shaped areas indi- 

 cating air chambers. Z?, a young sporophyte 

 within the parent archegonium: the region 

 which is to become the spore case is indicated 

 by the cross lines, and the small foot is at- 

 tached to the base of the archegonium; e, a 

 special envelope developed around the arche- 

 gonia of Marehantia 



