374 Wulist: BRANCHED PROTHALLIA 
wall where the light conditions were good and the prothallium 
was not crowded by other prothallia. Fic. 9, A, shows a young 
branched prothallium of about twenty cells, which had formed a 
filament of three cells in the usual manner before the expanded 
portion of the prothallium developed. The second cell of this 
filament gave rise to a filamentous branch of three cells; the ter- 
minal one of which divided by two oblique longitudinal walls to 
form the beginnings of an apical cell. From the first cell of the 
branch was cut off laterally a cell which would later develop into 
FiG.9. Branched prothallia of Asplenium Filix-femina (L.) Bernh., X 75:- 
another branch. The expanded portion of the prothallium also 
gave rise to a short filamentous branch of two cells. 
In Fic. 9, B, a short filament of three cells was first formed by 
transverse divisions, then the third cell divided in such a manner 
as to form the beginnings of an apical cell. In the meantime a cell 
was cut off laterally from the first cell of the filament. By trans- 
verse and longitudinal divisions this branch developed becoming 
two cells in width and forming at the apex the beginnings of an 
apical cell. An extreme case of branching is shown in FIG. 9, G 
4 filament of three cells formed in the usual manner. From the 
