12 
Ohio Biological Survey 
Only a very small proportion of the many groups of ascomycetes 
has been studied with respect to sexual reproductive areas and life 
histories in general, and much of the work accomplished is preliminary, 
fragmentary, unconlirmed, and unsatisfactory. In all present arrange¬ 
ments of ascomycetes, we hnd occasionally in juxtaposition families or 
larger groups that have very different reproductive tracts; and further 
studies are certain to reveal more of this sort of inconsistency in systems 
of classiheation based largely on spore characters and mature conditions 
of ascocarps. However, one cannot make very great changes based on 
the comparatively few and often fragmentary and uncertain researches 
that have been made. For example, the lichens must be interpolated, 
for the present, in large groups among other ascomycetes, though they 
mav need further distribution after we know more about life histories. 
The general similarity of the reproductive tracts in a large majority of 
the lichens that have been studied, the resemblance of the somatic tracts 
in large groups of lichens, and the rather limited knowledge of the rela¬ 
tionship between lichens and other ascomycetes justify this conservatism 
in distribution. 
In previous arrangements of ascomycetes in a single system, no dis¬ 
cussion of possible or probable homologies and relationships has been 
attempted. With our present limited knowledge, such discussion must 
serve as an argument for the method rather than a very great help in the 
arrangement. Unfortunately, we must continue to base our taxonomic 
treatment of ascomycetes quite largely on spore characters and on the 
structure of mature fruits until we have sufficient data to enable us to use 
more fundamental characters. However, in the plan of classification to 
follow, the Lccanoralcs have been kept distinct from the Pczizalcs, partly 
because the lichens that have been examined from the former group have, 
on the whole, a similar type of reproductive organs, more complicated 
than those in the latter group, in which these tracts are as a whole more 
degenerate, or possibly more primitive. Which of these two orders 
should stand higher is still an open question, regarding which certain 
statements are made below. For the present, we have placed the order 
which has the more specialized somatic structure higher. However, it is 
readily admitted that the higher form of vegetative structure may indi¬ 
cate either less of degeneration or a better development because of the 
advantageous conditions under which the lichens live. Again, if the 
Ascomycetac have arisen from the Rhodophyceae, a consideration to be 
taken up below, the Lecanorales may yet be proved to have, as a whole, 
a shorter line of descent than the Pezizales. 
