372 Harper.—Sexual Reproduction in Pyronema 
known of sexual fertilization elsewhere, the conclusion is 
inevitable that we have here also a true sexual reproduction. 
Cells of separated origin fuse by means of the breaking down 
of cell-walls and the union of protoplasmic masses at the 
point of contact, and this protoplasmic union is followed later 
by a pairing of the nuclei. These facts are conclusive as 
to the homology of the processes here with the sexual pro¬ 
cesses in Cystopus, Oedogonium , Nemalion , Batrachospermum , 
&c., and it seems hardly necessary to discuss the assertion 
that such fusions are the same as those which occur between 
the ordinary vegetative hyphae of a. mycelium. I have dis¬ 
cussed the significance of these latter fusions elsewhere ( 17 ), 
but it only needs a moment’s consideration to show, that 
they have no direct relation with the sexual conjugation 
I have above described. These mycelial fusions are not 
between specially differentiated hyphal cells. They occur 
at no definite point in the life-history of the Fungus, and 
lead to no specific fruit-formation. Indeed the comparison 
is so shallow and unenlightening, even on the basis of 
Tulasne's original description of the fusion in Pyronema 9 
that it is hardly worthy of a detailed consideration. 
Van Tieghem ( 3 - 7 , p. 1166, note) has brought forward the 
argument that the methods of sexual reproduction, as de¬ 
scribed for the Lichens, Mildews, Eurotium , Pyronema , &c., 
are too varied to be found in related genera of such a group 
as the Ascomycetes. Such a priori arguments are of very 
little value in connexion with a subject so little investigated 
as the sexuality of the Ascomycetes, in which the number of 
forms whose ascus-fruit development has really been thoroughly 
investigated is so small in comparison with those in which, 
because of their small size or the difficulty in separating the 
Fungus from its substratum, &c., the course of this develop¬ 
ment in its earlier stages is largely unknown. For the present 
we shall have to admit that whether it is reasonable or not 
there are in the true Ascomycetes at least such types of 
sexual apparatus as have been described for the Laboul- 
beniaceae, the Lichens, the Mildews, and Pyi'onema. It is 
