IN THE POLYPODIACEAE 



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apical growth was present in all of them. The branched prothallia 

 shown in Figs, i, A-F; 2, G-J; 4, N-Q; and 5, R-T, developed 

 on the distilled water cultures, while those in Figs. 2, K; 3, L, M; 

 and 5, U, developed close to the inner pot wall on the soil cultures. 

 Fig. I, 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 transversely until three and five cells 

 were formed before they developed an expanded region. In 

 Fig. I, 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. FiG. i, D, shows not only the develop- 

 ment of a branch from the second cell of the filament but also 



Fig. 4. Branched prothallia of Onoclea sensibilis L., X 12 = 



the tendency of the prothallium to revert to a filamentous stage 

 after a small plate of cells has been formed, if the nutrition 

 is not sufficient to meet its needs. In Figs, 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. Fig. 2, I, J, shows 

 pronounced cases of dichotomous branching which occurred where 



