IN THE POLYPODIACEAE 375 
second cell there was cut off laterally a cell which developed im- 
mediately by longitudinal and transverse divisions into an ex- 
panded branch with a definite growing region at the apex. 
The third cell of the original filament divided by a longitudinal 
division into two cells, a larger and a smaller one. From the 
larger of these two cells a branch developed which formed another 
expanded prothallium whose growing point was not definitely 
marked. In the meantime the growth of the primary prothallium 
had continued and an expanded part was formed showing a 
decided tendency to branch dichotomously at the apex. 
Et) 
RUN 
Sea 
Fic. 10. A, B. Branched prothallia of Asplenium bulbiferum Forst., X 75- 
C. Branched prothallium of Asplenium platyneuron (L.) Oakes, X 75- 
Asplenium platyneuron (L.) Oakes.—Fic. 10, C, shows a pro- 
thallium of this species which developed in a crowded region ona 
soil culture. In} this case branching occurred at a later period in 
the development of the prothallia. No filament was formed in 
the early development of the prothallium, but the second cell by 
division gave rise immediately to the beginnings of an expanded | 
cell plate which during development branched dichotomously. 
Each branch in turn formed a distinct growing region at its apex. 
