Classification of Ohio Ascomycetes 5 
(Fink 31). With this hypothesis falls the argument that lichens con¬ 
stitute a special biological group, nor can classihcation consistently con¬ 
sider such groups in any event. Some botanists have supposed that we 
must know the relation of every lichen or every group of lichens to a 
non-lichen ancestor with some degree of certainty before we attempt 
to distribute lichens, but this position is manifestly erroneous. Phyl- 
ogeny is a science of probabilities, and such exact knowledge of rela¬ 
tionships has not been attained in any group of plants of considerable 
size. Lichens resemble other ascomycetes in their methods of sexual 
reproduction, and their special manner of vegetative reproduction by 
soredia and soralia can have no considerable weight in favor of treat¬ 
ment as a distinct group of plants. Higher lichens exhibit certain pecul¬ 
iarities of vegetative structure, due to their parasitism on algie; but 
their fruits are like those of other ascomycetes, which in turn vary 
greatly with respect to somatic structure. In view of the facts regarding 
the reproductive tracts and the fruits, the peculiarities in regard to 
somatic areas are not sufficient ground for distinct consideration of 
lichens, especially since they are connected with other ascomycetes by 
hundreds, if not thousands, of intermediate orders, genera, or species. 
Present separate incorporation of lichens in herbaria, the large litera¬ 
ture of lichenology, and the fact that students of ascomycetes, for most 
part, may be divided into two groups, those who study lichens and those 
who study other ascomycetes, present real obstacles to be overcome; but 
arguments of expediency and temporary convenience are hardly valid 
reasons for maintaining a system of classification that is not in accord 
with present knowledge regarding the structure, the ontogeny, and the 
probable phylogeny of ascomycetes. For this reason, many botanists 
who have considered the matter carefully believe that our method of 
treatment, which is, in spite of temporary inconvenience, in accord with 
knowledge of the ascomycetes, should he followed in any systematic 
treatment of the whole group. 
There are many genera of ascomycetes which contain some lichen 
and some non-lichen members, and, as stated above, the bridges that 
connect ascomycetous lichens with other ascomycetes are many. The best 
way to facilitate comparison of these forms and thus strengthen our 
knowledge of the ascomycetes as a whole is to treat the group as a unit. 
This is, without doubt, also the best way to express what is known 
regarding these fungi. 
Some of the points of nearest approach of lichens to non-lichen 
ascomycetes are the following. Endomyccs scytoncmatum is a lichenoid 
