BASCOMBE BRITT HIGGINS 
same time. In like manner the ascospores, but not the Cylindro- 
sporium conidia from P. serotina, would infect P. virginianum or P. 
mahaleb plants. 
Plants of P. serotina, P. virginiana, and P. americana have several 
times been inoculated with ascospores and conidia from P. avium 
but no infections have ever been obtained from such inoculations. 
Likewise no infection has ever been produced on P. avium by either 
ascospores or conidia from P. virginiana or P. serotina. 
During the last weeks of April of this year a large series of cross 
inoculations were made in another greenhouse on all the different 
species before mentioned; but these resulted in almost total failure, 
probably because of the low temperature of the house. No infections 
were obtained except with the organism from P. virginiana and P. 
serotina. Only the Cylindrosporium conidia from P. virginiana were 
used and no infections were obtained except on P. virginiana where 
infection was rather abundant. Both ascospores and conidia of P. 
serotina were used. From the conidial inoculations infections occurred 
on P. serotina only. The ascospores however produced infection on 
P. serotina, P. virginiana and P. mahaleb. 
The leaves of P. virginiana have also been infected with a pure 
culture obtained from conidia of the Cylindrosporium on the fruits 
of the same species. This shows that one species is capable of infecting 
both leaves and fruit of this host. 
Systematic 
The study of morphological and cultural characters of Cylindro- 
sporium from the various host species showed some slight variations, 
but none which were prominent or constant enough to be of specific 
value. It was thought, therefore, before a comparison of the perfect 
stage from the different hosts was made, that there was but a single 
species with several more or less distinct forms on these hosts. 
Relation of Species of Cylindrosporium to the Natural Subdivisions 
of Prunus. — A careful study of the ascogenous stage from the different 
hosts showed that there were marked and constant differences by 
which the forms might be divided into three distinct groups. The 
first group includes all those which have the type of development 
found on P. avium (in which the ascocarp extends from one epidermis 
of the leaf to the other in contrast with those in which the ascocarp is 
