14 
Ohio Biological Survey 
until our information is greatly increased so that many facts which have 
a bearing on classification may be known and considered in correlation. 
Our knowledge of the development of the ascocarp is perhaps even 
more fragmentary than that of the sexual apparatus, toward which a 
large portion of the recent work has been directed. It is still an open 
question whether the cleistothecium, the perithecium, or the apothecium 
is the most primitive form of the ascocarp; and the whole development 
of many carpologic structures in various groups of ascomycetes must be 
carefully studied before we may know their worth as criteria for con¬ 
structing a system of classification. 
The Besseys (8 and 9) think that there is good reason to believe that 
Collcma-\\kt plants with apothecia, like the one studied by Miss Bachman, 
may be the most primitive of existing Ascomycetae and closely related 
to the Rhodophyceae. This suggestion seems reasonable since the species 
of Collcma and Miss Bachman’s plant are low forms of lichens vegeta- 
tively, the thalli being mycelia devoid of plectenchymatous structure, 
while the plants are apparently near relatives of such families as the 
Lccideaccac, the Gyalectaceae, and the Ascoholaceac, all of which may be 
rather primitive ascomycetes. Of these groups. Miss Bachman’s plant 
and Ascobolus carbonarius, studied by Dodge, are nearest the 
Rhodophyceae of those that have been examined with respect to repro¬ 
ductive tracts, and may well be regarded as the most primitive ascomy¬ 
cetes whose life histories have been investigated. Of the two plants. 
Miss Bachman’s, on account of the character of its male reproductive 
organs, appears to be nearer the Rhodophyceae. Yet the view that the 
first ascomycetes were algicolous is opposed to the one commonly held 
by botanists to the effect that lichens may be traced back to non- 
algicolous ascomycetes. If the theory that the most primitive ascomy¬ 
cetes are those having apothecia be true, of course much more investiga¬ 
tion is needed before we can safely decide whether the primitive forms 
were lichen or non-lichen. If lichen, it may be that we have the most 
primitive of existing forms among such members of the Collemaceae as 
possess the low vegetative structure noticed above and reproductive 
tracts and sexual behavior most like those known in the Rhodophyeeae. 
The primitive forms are probably to be sought among those that live in 
loose relationship with the algal host, but are still largely dependent on 
this host. The Collemaceae fulfill these conditions, since they do not, 
with one or two exceptions, form haustoria, but simply penetrate through¬ 
out the gelatinous Nostoc colonies, confining their course to the sheaths 
and scarcely injuring the protoplasts, while they are but weakly attached 
