PYRONEMA. 115 
pass at once into the odgonium, to the central mass of egg-nuclei, and 
become mingled with them (Fig. 43, F). The number of male nuclei 
entering the oogonium does not seem to be exactly the same as the 
number of egg-nuclei to be fecundated. Both sexual organs arise as 
multinucleate cells, and, as there is no evidence subsequently of a 
parallel series of nuclear divisions in each, it is difficult to see how 
exactly the same number could be provided in each organ. 
Only a small portion of the cytoplasm of the antheridium passes 
into the egg-cell, so that here, as elsewhere in the plant kingdom, the 
superior significance of the nuclei in fecundation is strikingly mani- 
fested. The male and female nuclei mingled in the central group are 
indistinguishable in size, structure, and staining qualities, so that it is 
0 
Fic. 43.—Fusion of sexual nuclei in the oégonium of Pyvonema.—(After Harper.) 
F, basal wall of trichogyne dissolved, male and female nuclei collected in dense mass 
in center of odgonium and fusing in pairs; nuclei still present in trichogyne and 
upper end of antheridium ; 4 hyphz budding out from oégoni 
G, group of fusing nuclei from central mass of nuclei in an odgonium. 
impossible to pick out a single nucleus and say whether it has come 
from the oogonium or antheridium. The nuclei fuse in pairs while 
they are aggregated in the dense mass (Fig. 43, G). The behavior 
of all the nuclei in the center of the mass was not determined with 
certainty, but there is every reason to believe that the rule of fusion 
in pairs holds for nearly the whole mass. Harper expressly states that 
there is no general fusion of the nuclei into a single mass, as can be 
clearly seen when the nuclei scatter after fusion. 
The odgonium of Pyronema functions at once as an ascogonium, 
All fecundated nuclei pass into ascogenous hyphe and may reach the 
asci. Here the young ascus develops also from the penultimate cell 
of a bent ascogenous hypha, and in it two nuclei are present which 
