Allen-—Spermatogenesis and Apogamy in Ferns. 25 
.growth may begin as a filament and then broaden into a strap, 
or it may continue as a filament and branch, much in the 
fashion of the prothallium of Trichomanes as described by 
Bower and others. All of these adventitious prothallia bear 
rhizoids and glandular hairs and antheridial sacs. In one case 
I saw a filament thirty-five cells long with a side branch three 
cells long. Scattered along its length were nine antheridial 
sacs. Ho indication of a sporophyte has been observed on any 
of these secondary prothallia. 
Cell and Nuclear Fusion in the Sporange of Aspidium 
Falcatum. 
In the light of Farmers and Digby’s discovery of nuclear 
migration and fusion in the tissue of the prothallia from which 
the young sporophyte arises in Lastraea pseudo^mas var. poly- 
daclyla, the possibility of the existence in other apogamous 
ferns of vegetative fusions replacing normal fertilization, must 
be especially considered. In Aspidium falcatum I find a sub¬ 
stitution fusion in the sporanges. The sixteen spore mother 
cells fuse in pairs to form eight much larger cells which then 
undergo the reduction division. 
The development of the sporanges and sporogenesis pro¬ 
ceeds normally up to the point at which fusion takes place. In 
the first eight-celled stage the spore sac is small. The cells of 
the two-layered tape turn are still intact. They are fitted closely 
to each other and occupy their original position. The nuclei of 
the tapetal cells are dense and stain heavily but the cells do 
not show marked signs of degeneration. The eight cells of the 
sporogenous tissue are angular and pressed closely against each 
other, leaving no intercellular spaces. The equatorial plate 
stage of the division of these eight cells is shown in figure 
forty-two. The cell was one of eight which were passing simul¬ 
taneously through the last division before the formation of the 
spore mother cells. The cells at this stage are still angular, 
fitting closely to each other and to the walls of the inner layer 
of tapetal cells. The cell walls, if present, are very thin and 
delicate. The cytoplasm here is dense and the vacuoles are 
