370 WuIst: BRANCHED PROTHALLIA 
the filament usually gave rise to the expanded portion of the pro- 
thallium. In both of these cases the branches originated in the 
third cell of the filament. In Fic. 2, J, the group of cells at the 
apex between the branches indicate that there will be a continu- 
ation of the main growth of the prothallium. In Fics. 2, K, and 
3, L, M, dichotomous branching developed at a slightly later stage 
after the first divisions of the expanded portion of the prothallia 
had been formed. Fic. 4, N-Q, show single lateral branches which 
appear to have originated at about the same period in the de- 
velopment of the prothallia as the dichotomous branches shown 
in Figs. 2, K, and 3, L, M. Fic. 5, R, S, shows branches de- 
veloped from the expanded portions of the prothallia. In Fic. 
R 
T 
Fic. 5. Branched prothallia of Onoclea sensibilis L. R-T, XK 125; U, X 75- 
5, R, the branch formed a plate of cells while in Fic. 5, S, it 
tended to assume a filamentous character. Fic. 5, T, shows 
another case of dichotomous branching but at a later stage in the 
development of the prothallium. Here it occurred at the apex of 
the expanded region of the young prothallium. Fic. 5, U, is 
unique in that the branch appears to have originated in the first, 
second and third cells of the filament. 
