234 ILLINOIS ACADEMY OF SCIENCE 
examined. Sydow and Theissen think that this character is 
evident only in mature material and only at a definite stage of 
ripening. 
The specimens examined have apparently a conspicuous 
perithecial wall. The Dothidiaceae are generally character- 
ized by perithecia reduced to mere cells in the stromata, but 
Brefeld’ says, ‘‘Phyllachora is unusual in that it has a definite 
perithecial wall.” Ellis and Everhart’ call the perithecia in 
Phyllachora graminis ‘‘ascigerous cells.” Jaczewski’ illustrates 
P, gramims by a drawing in which no perithecial wall is shown 
but in the descriptions of P. graminis by Winter”, Lindau”, 
Frank’, Brefeld’, and by Kirchner-Boltshauser’, a definite peri- 
thecial wall is mentioned. Sydow and Theissen” explain the 
apparent presence of a perithecial wall by the fact that the 
function of the lacking wall is taken over by the inner stro- 
matic surface surrounding the loculi. For this purpose the 
stromatic elements undergo special orientation which in P. 
gramimis takes the form of a thickening and by reason of a 
darker color due to this thickening an actual perithecial wall is 
simulated. 
The form of the perithecia varies from oval to angular, be- 
ing modified by pressure during development. Young and 
old perithecia grow together in the same stroma, and the 
number in a single stroma has been considered as a specific 
character only in extreme cases in the Phyllachoraceae, al- 
though it is regarded as a distinguishing character in the 
Polystomellaceae. 
Spore measurements, of use in systematic diagnosis, vary 
considerably in the species. The following tabulation gives 
graphically the spore length of measurements made from ex- 
siccati of P. graminis on different hosts. A few other species 
of Phyllachora are included for comparison. The solid line 
represents the minimum and the entire line the maximum spore 
strength. Where there are double lines, the upper one repre- 
sents spore measurements taken from Saccardo’s “Sylloge 
Fungorum.” 
It is noteworthy that P. cynodontis and P. graminis have 
identical spore measurements in the “Sylloge Fungorum.” The 
same spore measurements for these species were obtained from 
herbarium material. P. sphaerosperma has the same maxi- 
