330 Harper.—Sexual Reproduction in Pyronema 
produces the ascus. This difference, as well as Dangeard’s 
failure to find the conjugation of the antheridial cell and 
oogonium, is due, I am convinced, to the fundamental weakness 
of his method of studying the young fruits. I have repeatedly 
proved in my own experience, as have many others, that it is 
impossible to get clear views of the fruits, resting as they 
regularly do on and in an intricate web of vegetative hyphae, 
except by slicing this mass into thin and transparent micro¬ 
tome-sections. 
To the second general question noted above, as to whether 
the sexual apparatus described is functional, Dangeard replies 
in the negative. He fails to find any evidence of a conjugating 
pore between the antheridium and oogonium. In some cases 
the antheridial cell and nucleus degenerate early while the 
oogonium is still uninucleate, though in others the antheridial 
nucleus is still to be found in the antheridium after two nuclei 
are present in the ascogonium ; Dangeard claims to have 
examined so much material that this purely negative result 
must be accepted as a final and indisputable proof that the 
conjugation which he fails to find does not exist. In spite of 
this certainty, however, I am quite convinced that a more 
protracted and painstaking search and better methods would 
have brought to light the stages in development which 
Dangeard failed to find. Any one who has worked on 
fertilization-phenomena, either in plants or animals, knows 
how extremely difficult it is to bring together a complete 
series of the stages involved, and that negative evidence in 
such cases has very little weight. De Bary attacked the 
problem with essentially the same methods of preparation as 
were used by Dangeard, and failed at exactly the point at 
which Dangeard has failed, that is in discovering the con¬ 
jugation-pore between the male and female cells. Dangeard’s 
investigation leaves the problem where De Bary left it. 
Wager (40) has pointed out the possibility that Dangeard 
had a parfhenogenetic form of Sphaerotheca before him, but 
I am not inclined to accept this view, and am still convinced 
that he has failed to find the fertilizatiomstages because 
