acteristic of the normal sporangia 
1910] PACE—FERN PROTHALLIA 55 
all the antheridia only one layer of wall cells is present, and these 
are few and rather definitely placed. But this structure shows two 
distinct layers (figs. 9, 10), except in one section, and this at only one 
place (fig. 11). Here for the 
space of two cells the wall is 
only one cell thick, but these two 
cells might divide and make the 
two layers complete. The outer 
layer consists of many cells, which 
always contain chloroplasts, but 
the next layer contains chloro- 
plasts in a few cells only. The 
nuclei in this second layer are 
quite different from those in the 
interior, and in some of the cells 
there is a suggestion of the usual 
tapetal appearance. It does not 
have the long slender stalk char- 
of the higher Polypodiaceae, but 
it probably would have elon- 
gated somewhat before maturity, 
making it very similar to the 
stalks of the Osmundaceae. Con- 
sequently, this structure is quite 
unlike an antheridium, and is 
almost perfect in its sporangial Fic. 11.——A small portion of the same 
characters. As there were nO sporangium-like structure shown in fig. 9, 
mitotic figures, it could not be _ but from another section; this is the only 
determined whether the nuclei —_ Le see 
contained the sporophytic or might divide and make the two layers 
gametophytic number of chromo- complete. 
somes, but we should expect 
the sporophytic number to appear, especially since another pro- 
thallium bore a mature sporangium of the Osmunda, type, with a 
few spores still remaining in the sporangium. In the absence of 
mitotic figures, such a sporangium easily invites speculation. It 
