252 THE AMERICAN NATURALIST. [Vor. XXXIX. 
first account of this phenomenon describing it for several forms. 
The mother cell of an ascus sometimes terminates a hypha but 
more commonly is situated a little back from the end at a point 
where the hypha bends abruptly like a knee. The mother cell 
contains two nuclei, closely related to each other, that unite, 
after which the fusion nucleus divides to form the ascospores. 
Dangeard considered this fusion to be a sexual act and the 
product an oóspore which germinates immediately to form the 
ascus. He regards the ascus as a sporangium, and equivalent 
to the promycelium which he calls a conidiophore. Dangeard 
is not willing to accept any of the evidence that the ascocarp 
ever results from a sexual act or that sexual organs either func- 
tional or abortive are present at any stage in the life history of 
Ascomycetes. Sexuality, according to him, is reduced to the 
fusion within the ascus alone. He (Dangeard, '96—97a, b; 
: 00) discredits the work of Harper on Sphzrotheca, Erysiphe, 
and Pyronema and the older accounts of De Bary and his pupils 
on sexual organs of the Ascomycetes. A series of short papers 
in Le Botaniste (: 03, Fas. 1) presents Dangeard’s last attack on 
the work of Harper and a reaffirmation of his peculiar views. 
Harper's description of sexual processes in Spheerotheca ('95 ; 
'96) Erysiphe ('96), and Pyronema (:00b) are so convincing 
that, together with our knowledge of sexual organs in the 
lichens, Laboulbeniales, and Gymnoascales, we must accept the 
old view of De Bary that the ascocarp represents a development 
(probably sporophytic) from a sexual phase even though it may 
be established that there is much apogamy in the Ascomycetes. 
Harper gives the clearest account of the nuclear fusion in the 
ascus of any author without, however, committing himself to 
speculations on its significance. The subject is well sum- 
—_— a on Pyronema (:oob, pp. 363, 394). He 
‚ Fyronema, and some other forms that the 
ascus is always developed from a penultimate cell of a hypha 
which bends sharply so that this cell appears to lie at the tip. 
There are two nuclei at the end of the ascogenous hypha and 
these divide simultaneously in a very characteristic manner so 
that the young: ascus receives two of the resultant four nuclei, 
but each is derived from a different one of the original pair and 
