MARCHANTIA POLYMORPHA 195 



of a wall, one layer of cells in thickness, which surrounds and 

 incloses a large, naked, nucleated ovum. 



XI. Cut vertical sections through a female branch of like 

 age to the above : treat as before, and observe in median 

 sections 



1. The stalk, on which is borne 



2. The terminal stellate head. 



3. That the latter consists of tissues similar to those of the 

 vegetative thallus : thus there may be seen 



a. The superficial " epidermis," and " stomata." 



b. Air-cavities with chlorophyll-parenchyma. 



c. Large mucilage-cells. 



4. The archegonia, which are flask-shaped bodies suspended 

 in an inverted position : note in a mature archegonium 



a. The long neck, consisting of many tiers of cells, which 



together form a single-layered cylinder surrounding 

 the channel of the neck : when, mature the neck will 

 be seen to be open at its apex. 



b. The more distended lower ventral part of the arche- 



gonium, also surrounded by a single-layered wall, and 

 attached by a short massive stalk to the receptacle. 



c. Pay special attention to the contents of the ventral por- 



tion : in the mature archegonium the cavity will be 

 seen to be occupied by a single primordial cell the 

 ovum or oosphere to which access is gained from 

 without through the channel of the neck. 



XII. Keep some specimens of Marchantia^ having mature 

 male receptacles, protected for some days from access of water 

 from above : then place a drop of water on the upper surface 

 of a receptacle, and after a short time transfer it to a glass 

 slide, and examine under a high power ; there will then be seen 

 numerous motile spermatozoids of elongated, slightly curved 

 form, and they are kept in active motion by two cilia attached 

 to the anterior end. In order to make them clearly visible 

 they should be killed and stained by adding a small quantity 

 of iodine solution, or of osmic acid. 



XIII. Add a drop of water containing living spermatozoids to 

 a fresh preparation of a female receptacle containing mature 



O 2 



