374 PRACTICAL BOTANY 



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." 

 I. 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 



archegonium, also surrounded by a single- 

 layered wall, and attached by a short mas- 

 sive stalk to the receptacle. 



c. Pay special attention to the contents of the 



ventral portion : 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. 



It is perhaps easier in these plants than in any others to trace 

 the successive stages of development of the archegonium : this 

 may be done by cutting sections, similar to those above described 

 from young female receptacles, and noting first those archegonia 

 which are situated nearest to the stalk ; these should then be 

 compared with those further removed from it, which will be 

 found to represent successively older specimens : thus the 

 several stages of development may be traced even in a single 



