IN THE POLYPODIACEAE 369 
apical growth was present in all of them. The branched prothallia 
shown in Fics. 1, A-F; 2, G-J; 4, N-Q; and 5, R-T, developed 
on the distilled water cultures, while those in Fics. 2, K; 3, L, M; 
and 5, U, developed close to the inner pot wall on the soil cultures. 
Fic. 1, A, D, shows branched prothallia whose branches originated 
in the second cell of the filament. In these prothallia the branches 
tended to form immediately a plate of cells, while the cells of the 
filaments continued to divide trans ly until three and five cells 
were formed before they developed an expanded region. In 
Fic. 1, B, C, while the first branches developed from the second 
cell of the filament, later branches were given off by the expanded 
portions of the prothallia. Fic. 1, D, shows not only the develop- 
ment of a branch from the second cell of the filament but also 
Fic. 4. Branched prothallia of Onoclea sensibilis L., X 125. 
m to revert to a filamentous stage 
the tendency of the prothalliu 
en formed, if the nutrition 
after a small plate of cells has be 
is not sufficient to meet its needs. In Fics. I, F; and 2, G, H, 
it seems characteristic for the first branch to originate in the third 
cell of the filament. However, other branches developed from 
the more expanded portion of the prothallia. Fic. 2, 1, J, shows 
pronounced cases of dichotomous branching which occurred where 
