MARCHANTIA POLYMORPHA. 75 



b. The encircling tissues, indented at one point, yet 

 continuous ; notice further 



The internal portion of uniform parenchyma. 

 The external row of air cavities, containing 

 chlorophyll-bearing filaments, and provided 

 with stomata, essentially like those of the 

 pedicel, 

 iii. Papillary trichomes arising from many of the 



epidermal cells. 



Using an immature branch, cut a transverse section 

 across two or three rays nearer the center of the head and 

 passing through the groups of sporogonia, notice 



c. The central cavity, much smaller than in the rays. 



d. The right and left sides, which instead of being 

 united, are prolonged into the perich&tium, so 

 that the perichaetial leaf on the right side of the 

 group of sporogonia belongs to the left side of 

 the right hand ray, while the perichaetial leaf on 

 the left side belongs to the right side of the left 

 hand ray. 



e. The section of the perichaetial leaves, one cell in 

 thickness, or sometimes two at the base. 



/. Examine the flat surface of the perichaetium, the 

 shape of the cells, and the notched and fimbriated 

 margin. Draw. 



g. The bent filaments, paraphyses, composed either 

 of a single row of cells, or of two or more 

 united rows for part or the whole length. 

 Draw. 



3. The archegonia, 6 the flask-shaped bodies among the 

 paraphyses, consisting of 



6 Bear in mind that the archegonia are called sporogonia after fertiliza- 

 tion and a certain amount of growth has taken place. 



