MARCHANTIA POLYMORPHA 369 



3. Unicellular outgrowths or hairs, with mucilaginous 

 walls. 



Trace under a high power the process of development of the 

 gemma. It may be seen that the gemma originates as a unicellular 

 papilla, which divides first into two cells : the lower remains 

 quiescent as the unicellular stalk, while the upper cell grows and 

 divides, ultimately giving rise to the mature gemma. Trace the 

 succession of cell-divisions by comparison of gemmae of various 



Removing some gemmse from the cups, germinate 

 them on clean moist sand under a bell-glass at a medium 

 temperature, and exposed to the 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 indentations serving as 

 an organic apex : from the lower surface root-hairs Lave 

 been formed, by simple outgrowth of single cells. After 

 growth has been continued for a longer time the 

 differentiation of tissues characteristic of the mature 

 thallus, with " stomata" and air-cavities, becomes appa- 

 rent on the upper surface, the thallus thus assuming 

 a dorsiventral character. 



No gemmse are produced in Pellia. 



The Male Branch (Antheridiophore) 



IX. Having noted the general form of the male 

 branch of the thallus, with its stalk and terminal disk, 

 cut transverse sections of the stalk, mount in glycerine, 

 and examine under a medium power. Observe 



1. The circular outline of the sections. 



B B 



