380 



WuisT: Branched prothallia 



cells had begun to develop, while in Fig. 15, E, F, branching oc- 

 curred much later in the development of the prothallia. 



Pteridmm aqidUnum (L.) Kuhn. — The only example of branch- 

 ing observed in this species was on Prantl's full solution (Fig. 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 



Fig. 15. E-G. Branched prothallia of Woodwardia virginica (L.) Sm., X 75; a, 

 antheridia. H. Branched prothallium of Pteridhim aquilinmn (L.) Kuhn, X 125. 



main filament developed three cells of irregular length before 

 cutting oft' 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 



