346 Harper.—■Sexual Reproduction in Pyronema 
demonstration of a true fertilization, involving the fusion 
of male and female cells, was hence incomplete. Kihlmann’s 
statement, that true fertilization in Pyronema was still only an 
hypothesis, was in a sense justified from the facts as he was 
able to work them out. For De Bary who, at the time he 
worked on Pyronema , believed in the possible transmission 
of a fertilizing influence through a cell wall and without 
fusion, the case was easier. As a matter of fact, as is shown 
in Figs. 15 and 1 5 a, the second fusion between the base 
of the conjugating tube and the oogonium does occur, and 
thus, as will be seen from the following description, all doubt 
as to the existence of sexuality in Pyronema disappears. 
If we examine now in detail the changes in the sexual 
apparatus after it has reached maturity; which lead up to fertili¬ 
zation, we shall find first of all, that an area of protoplasm 
in the antheridium, in the region where the tip of the con¬ 
jugating tube is pressed against its wall, is differentiated as 
a very finely granular disk, and that the nuclei have with¬ 
drawn from this region (Figs. 7-12). This finely granular 
area, although located in the antheridium, is quite similar 
in shape and consistency to the so-called mouth-piece or 
receptive spot seen on the oospheres of Oedogonium , Vaucheria , 
and other Algae. It is an irregularly lens-shaped mass of 
hyaline protoplasm aggregated at the point where the first 
fusion-pore is to be formed. If we examine the beak-like 
prolongation of the conjugating tube we find that it alsor 
contains no nuclei, and its protoplasm is also denser and more 
finely granular than that further back in the tube (Figs. 6 and 
9-12). The differentiation of the protoplasm here is not so 
conspicuous but is quite as characteristic as in the area 
opposite it in the antheridium, and it doubtless indicates 
the differentiation of a special receptive spot equivalent to 
the hyaline mouthpiece in the Algae referred to above. It 
is less conspicuous only because it is enclosed in the narrowed 
beak so that it cannot take on the characteristic lens shape. 
These areas are evidently especially differentiated as a prepara¬ 
tion for the process of fusion and may be regarded as a real 
