The Collemaceae of Ohio 
43 
often poorly developed, and in some instances it is discontinuous and 
recalls the conditions just noted for Synechoblastiis Haccidus. These 
two species bridge fairly well the gap between members of the 
Collemaceae which have no cortex and those which have one. Some of 
the material of Mallotiiim also showed a poorly developed and scarcely 
continuous cortical plectenchyma. 
Sweeping statements to the effect that paraphyses are uniformly 
simple in many families of ascomycetes are due to the careless manner 
in which the examinations are made. We have not studied a species of 
the Collemaceae in which branched paraphyses do not occur (Fig. 11). 
In instances in which it is difficult to ascertain the structure, maceration 
and examination with an oil-immersion lens will always reveal branched 
paraphyses, often in large numbers. Though simple paraphyses occur 
in all of the species that we have studied, branched ones sometimes appear 
to be more numerous than the simple ones when one makes a careful 
examination. 
The spores of the Collemaceae are hyaline and vary from simple 
ones to muriform conditions (Fig. 13). The occurrence of muriform 
spores in Collema and simple ones in genera that have a plectenchymatous 
cortex makes it probable that there are at least two lines of descent within 
the family, one expressed mainly in the spore evolution, and the other 
showing the spore evolution and also the development of a cortical 
plectenchyma. In separating Synechoblastus, with several-celled spores, 
from Collema, which has muriform spores, we are following the tendency 
among students of ascomycetes to give more prominence than formerly 
to spore characters, in limiting genera. A gradual evolution from simple 
spores to several-celled ones and from these to muriform types is well 
known in many groups of ascomycetes; and transitional conditions in 
which a species may have either simple or septate spores, or either 
several-celled or obscurely muriform ones are occasionally met. There¬ 
fore, one sometimes meets difficulties in using spore characters as 
taxonomic criteria in the Collemaceae and in some other ascomycetes. 
However, we have encountered no difficulty in the species treated in this 
paper. 
The Collemaceae are related, with respect to apothecial and somatic 
structure, to the Pannariaceae and tO' the Lecideaceae. The difference in 
structure of the thallus, in the Lecideaceae on one side and the Colle¬ 
maceae and the Pannariaceae on the other, is mainly explainable as a re¬ 
action to different hostal environment and to inorganic, substratic con¬ 
ditions. With respect to the sexual tracts, the Collemaceae are closely 
