MARCHANTIA POLYMORPHA 193 



Removing some gemmae from the cups, germinate them on 

 clean moist sand under a bell-glass at a medium temperature, 

 and exposed to moderate light : on examining them after five or 

 six days, they will be seen to be elongated transversely to their 

 original axis of growth, the base of each of the lateral indenta- 

 tions serving as an organic apex : from the lower surface root- 

 hairs have been formed, by simple outgrowth of single cells. 

 After growth has been continued for a longer time the differen- 

 tiation of tissues characteristic of the mature thallus, with 

 " stomata " and air-cavities, becomes apparent on the upper 

 surface, the thallus thus assuming a dorsiventral character. 



The Male Branch (Antheridiophore). 



VIII. Cut median vertical sections through the terminal disk : 

 mount in weak glycerine, and examine first under a low power : 

 observe 



1. The general outline of the section, with its flat upper 

 surface. 



2. The amphigastria and rhizoids attached to the lower 

 surface. 



3. The cavities in the tissue, of two sorts, both opening by 

 narrow mouths on the upper surface 



a. Air-cavities fundamentally similar to those of the vegeta- 

 tive thallus. 



b Flask-shaped cavities each containing one antheridium : 

 these also open by a narrow channel on the upper 

 surface of the disk. 



Look for a single ripe antheridium which has been cut through 

 longitudinally : having found one, examine it in detail under a 

 high power, and observe 



1. The short stalk by which it is attached to the base of the 

 cavity. 



2. The wall of the antheridium, consisting of a single layer 

 of thin-walled cells. 



3. The mother-cells of the spermatozoids of cubical form, 

 and small size, which together constitute a dense central mass. 



