98 Report oF THE BoTANIST. 
How many distinct species of the fungus there are is unknown; 
but the number is probably much smaller than the number of 
host plants. This must be determined largely by cross-inocula- 
tion experiments. Such experiments have been in progress for 
two years, but the report on this part of the investigation, as 
well as on several other features, will be reserved for a future 
publication. 
