2 
WALTER SPURGEON BEACH 
Little is known respecting the existence of biologic specialization in the 
genus Septoria. Except for a few instances (15, 22, 45), no cross-inocula- 
tions have been made to ascertain whether a Septoria, as found upon a 
particular host, is restricted to that host, or is more or less cosmopolitan 
and adaptive in its parasitism. In the literature at present one is confronted 
by two extremes of treatment: {a) closely similar species are described on 
the same host, e. g., Septoria lactticae and S. consimilis on Lactuca saliva, 
(b) more widely variant forms on distantly related hosts are described as 
representing one species, e. g., S. graminum on twelve or more genera of 
grasses, and a species of sedge. It is obvious that such practice is not con- 
sistent, and cannot adequately reflect the truth. 
The facts as presented above are illustrative of the present unsatisfac- 
tory status of the species not only of Septoria but also of many other genera 
of the fungi imperfecti. More accurate knowledge regarding host char- 
acters, morphological variation, and biological specialization is greatly 
needed from the standpoint of classification. The genus is the more worthy 
of study on account of its high economic importance. To study such a 
large genus as Septoria in culture, either upon the living hosts or upon 
artificial media, would require the time of many investigators. The present 
paper is intended merely as a contribution to the general problem as sug- 
gested above, and the investigations were conducted with the following 
leading objects: 
1. To determine the host range of as many species of Septoria as pos- 
sible in order to ascertain (a) whether morphologically similar forms from 
different hosts vary in host range, and (b) whether morphologically unlike 
forms ever have the same host range ; or in other words to ascertain whether 
any of the species available for study consist of a number of biologic forms, 
and whether any now listed as distinct species are identical. 
2. To compare disease characters, i. e., the host response to infection, 
when produced (a) by a single species of Septoria upon dissimilar hosts, or 
{b) by different species of Septoria on the same host. 
3. To note any morphological changes in the size and shape of spores 
and pycnidia as a result of change of host or the condition of the host, or of 
other environmental factors. 
4. To determine the susceptibility of different parts of the same host 
and of these at different stages of 'maturity, and to note whether any dis- 
tinctions in disease characters are correlated with host structure and con- 
dition. 
Historical Review 
The literature dealing with biologic specialization is extensive. A com- 
prehensive review cannot be undertaken here, yet a brief summary of the 
essential points, especially as brought out by the investigations of rusts 
and powdery mildews, will be useful in the interpretation of the results to 
