146 
BASCOMBE BRITT HIGGINS 
This fungus was described by Karsten (17) in 1884 from leaves 
of Prunus padus; and Sorauer (13) states that in Europe the disease 
is confined almost entirely to this species. Aderholdt (i) in 1901 
said that the disease had been common on both sweet and sour cherries 
during the previous ten years. In America a disease attributed to 
this organism has been reported on nearly all species of Prunus both 
wild and cultivated. 
Because of the prevalence of the disease and its consequent econ- 
omic importance, it has seemed very desirable to know the complete 
life history of the fungus causing it. With this purpose in view an 
investigation has been in progress during the past three years, the 
results of which are here reported. 
For several years the disease has been very abundant in the 
vicinity of Ithaca, New York, on the sweet cherry (P. avium) and the 
wild choke cherry (P. virginiana). It has been found less abundant 
on the sour cherry (P. cerasus, P. mahaleb, P. pennsylvanica) , and on 
the plums (P. domestica, P. insititia, and P. spinosa). Through the 
courtesy of Professor J. G. Hall (now of Pullman, Washington) leaves 
of P. serotina affected with the disease were obtained from Clemson 
College, South Carolina, in August, 1912. A Septoria having spores 
only slightly different, but produced in a pycnidium, also found on P. 
pennsylvanica, was studied for comparison with these. The results 
of this study of Septoria will be reported in another paper. 
This abundance of material on a number of host species has made 
possible a comparative study of structural characters, relation to the 
host tissue, cultural characters, interrelations of the fungus on the 
different hosts, and its life history. Pure cultures of the organism 
from P. spinosa were not obtained, so that it could not be included in 
all the comparisons. 
Structural Characters 
The genus Cylindrosporium is characterized by having elongated 
colorless conidia borne on a more or less disk-shaped stroma just 
beneath the host epidermis. The acervuli on all the species of Prunus 
under observation agree with this characterization. The stroma is 
very delicate, at first consisting of one cell layer only, but becomes 
slightly thicker as the acervulus grows older. On the outer surface 
of this stroma short conidiophores give rise to conidia. They develop 
first over the center of the stroma and continue to develop centri- 
