IN THE POLYPODIACEAE 



379 



branch at one side of the apex. Fig. 13, C, shows the origin of a 

 branch from the apex of the expanded portion of the prothallium, 

 while Fig. 13, D, E, shows further development of such a branch. 

 These branches formed a small plate of cells, two rows in width, 

 then tended to revert to a filamentous condition, at the same 

 time growing downward, thus giving the appearance of two young 

 prothallia attached by their apexes. Fig. 13, F, shows the only 

 case of dichotomous branching which was observed. One of the 

 branches reverted from a plate of cells to a filament four cells in 

 length. 



Woodwardia virgifiica (L.) Sm. — The branched prothallia of 



Fig. 14. Branched prothallia of Woodwardia virginica (L.) Sm. 

 B, C, X 75- 



A, D, X 125; 



Woodzvardia virginica varied in size and shape and showed a 

 decided tendency to branch dichotomously. Those shown in 

 Fig. 14, A-D, and 15, E, F, developed on the inner surface of 

 the pot wall of the soil culture. They were not crowded by other 

 prothallia and were well lighted. Fig. 15, G, developed on Prantl's 

 nutrient solution with CaSO^ omitted. In Fig. 14, A, B, branching 

 took place from the first and second cells of the filament. In 

 Fig. 14, C, D, and 15, G, branching took place after the plate of 



