380 WulIst: BRANCHED PROTHALLIA 
cells had begun to develop, while in Fic. 15, E, F, branching oc- 
curred much later in the development of the prothallia. _ 
Pteridium aquilinum (L.) Kuhn.—The only example of branch- 
ing observed in this species was on Prantl’s full solution (Fic. 15, 
-H). Here the branch developed from the second cell of the 
filament and seemed to show a more vigorous growth than the 
main filament. The branch formed a short filament of two cells, 
then developed the beginnings of an expanded region while the 
Fic. 15. E-G. Branched prothallia of Woodwardia virginica (L.) Sm., X 75; % 
antheridia. H. Branched prothallium of Pteridium aquilinum (L.) Kuhn, X 125- 
main filament developed three cells of irregular length before 
cutting off the beginnings of an apical cell. This slowness in 
growth and the irregularity of length of the cells of the filament 
would seem to indicate a poorly nourished condition of the main 
filament. 
Discussion 
A comparison of the previously described branched prothallia 
with those found by other writers would seem to indicate that 
whatever factor, or set of factors, working separately or together, — 
may have been the determining ones, the development of branches — 
