88 MARCHANTIA POLYMORPHA. 



d. Make a vertical section through the base of the cup, 

 and observe stages in the development of gemmae. 



e. Draw. 



III. SEXUAL REPRODUCTION. 



1. The antheridial branch, and antheridia. 



Select an antheridial branch in which the stalk is rather 

 large and make a cross-section of it. Observe: 

 a. The general outline of the section. 

 6. The hairs which fill the grooves. Follow some of the 

 strands of the hairs downward and upward upon an 

 uninjured stalk and determine where they terminate. 



c. Sketch the section. 



Make radial vertical sections of the head, and observe: 



d. The prominent flask-like chambers, with their necks 

 opening upon the upper surface, each containing an 

 antheridium within it. 



e. The antheridium; its stalk; wall of one layer of cells, 

 within which are many squarish cells, the sperm mother- 

 cells. 1 



/. The air-cavities and tissues which compose the body 



of the head. 



g. Young and old stages of antheridia. 

 h. Draw enough of the section to show these structures. 



2. The archegonial branch, and archegonia. 

 Select both old and young branches, and observe: 



a. The appearance of young branches at the time they 



first may be distinguished from the thallus. 

 Then carefully dissect the young head and mount, or by 

 means of a radial vertical section observe: 



1 With fresh material often an abundance of swimming sperms may 

 be obtained. This may be done by placing a fresh ripe head in a 

 drop of water, at which time thousands of sperms may escape from their 

 antheridia. They may be studied first while moving, and then staining 

 with iodin will give an excellent view of their structure. 



