374 Harper.—Sexual Reproduction in Pyronema 
of his views can muster. Opposition to his view of the nature 
of the ascus-fruit in the forms he studied has not been based 
to any appreciable extent on detailed investigations of the 
development of these structures in the same or in related 
forms, but rather on a general scepticism as to the accuracy 
of De Bary’s observations, and on vague and fanciful hypo¬ 
theses such as those referred to above. De Bary’s generaliza¬ 
tion, as to the sexuality of all the Ascomycetes from the 
relatively few forms he had studied has been much criticized 
as based on too few observations. Still it is to be noted that 
no successful attempt has ever been made to subdivide the 
group in question. Regarding the group as a phylogenetic 
unit it was and is quite justifiable to assume that such similar 
structures as the ascus-fruits must be homologous, and if in 
one case their initial organs are a sexual apparatus, whether 
functional or not, the assumption is, until the contrary is 
proved, that the same will be true for the other members 
of the group, all due allowance being made for a possible 
suppression or further development of any particular stage 
in special cases. So long as there is no evidence from other 
sources on which to subdivide the group there is the strongest 
probability that the ascus-fruits of all Ascomycetes are 
morphologically equivalent to the ascus-fruits of Sphaerotheca , 
Pyronema , and the Lichens. 
The opponents of De Bary’s views, apart from Dangeard, 
who so far stands alone, have shown no less certainty of 
the unity of the group than did De Bary, and have con¬ 
cluded that the entire group is without sexual reproduction, 
because they believe functional sexual organs are lacking 
in some specific cases, although even in these the nuclear 
phenomena have not been yet investigated. Whether it may 
not be found after all that the Ascomycetes are a poly- 
phyletic group is still an open question, but at present, as 
heretofore, the evidence seems rather to point the other way. 
For the formation of sub-groups and the determination of 
their relationships the cell-structures of such forms as Euro - 
tium ) Xylaria , Claviceps , Pleospora , &c., in addition to those 
