20 
Ohio Uiological Survey 
and vegetative structure, though it is plainly seen that increasing knowl¬ 
edge of degeneration in the sexual areas and the sexual processes may 
soon require some modification of this method. Regarding the Phacidiales 
and the Hysterialcs, it is quite possible that further study may result 
in placing some of the lichens in the former order, nor is it certain that 
these orders are intermediate between discomycetes and pyrenomycetes. 
Concerning the angiocarpic groups, it is not probable that the perithecia 
and the cleistothecia all arose in similar manner, or that they are so 
closely related as the order adopted would indicate. The Pyrcmilales 
are placed after the non-algicolous groups for about the same reason that 
the Lecanorales are placed after the Pezisales. Here again, further 
studies are likely to require some modification of the method used herein. 
The Perisporialcs, the Aspergillales, the Exoascalcs, and the SaccJiaromy- 
cctales have been placed toward the close of the series since, if the theory 
of origin of the Asconiycctae from the Rhodophyceac be true, each of 
these orders, as a whole, seems to be composed of either degenerate or 
doubtful ascomycetes. Degeneration seems probable, on this basis of 
origin, in the simple reproductive tracts tending toward likeness in form 
and size of gametes, in reduction and final loss of the trichogynes, and in 
undoubted isogamy in a few instances among the saccharomycetes, 
though in this order the conjugati.^n, rarely observed, may be a 
secondarily acquired character. 
In closing, it should be stated that all speculations regarding the 
relationships of ascomycetes are rendered more uncertain by the prob¬ 
ability that carpologic evolution may have proceeded in nearly parallel 
lines in various groups so that forms that differ considerably with respect 
to archicarps and ascocarps may be more closely related than others that 
show considerable similarity with respect to these areas. 
In the studies of the orders and families of Ohio ascomycetes to 
follow in this series of papers, the better-known groups will be published 
while field work and laboratory investigations are increasing our knowl¬ 
edge of orders at present unknown to our flora, or poorly understood. 
The system of classification proposed herein will serve as a basis for the 
work and will indicate where each group studied is related in our scheme 
of classification adopted for the ascomycetes as a whole. The final work 
on the ascomycetes of Ohio should be to bring these studies together 
under a system of classification revised sufficiently to show the advance 
in knowledge of the group while the preliminary studies are in progress. 
The provisional arrangement which is to serve as a basis for the study 
of various groups of Ohio ascomycetes is given below. 
