384 BOTANICAL GAZETTE [JUNE 
The fungus which causes most cases of the disease is able to 
exist indefinitely in the soil by means of sclerotia, which may be 
formed either upon affected plants or by purely saprophytic 
growth in the soil and appear to form the usual, if not the only, 
mode of reproduction. 
This fungus may be exterminated by heating the soil. 
In exceptional cases the “drop” appears to have been 
caused by the conidial form of Botrytis vulgaris, but only in plants 
which were under unfavorable conditions. 
The disease may be caused by a typical form of Sc/erotinia 
Libertiana Fckl., but this is exceptional. 
In all cases of the disease there is the closest resemblance in 
the effect on the plant and in the parasitic mycelium which 
attacks it, the latter applying to the filaments and the organs of 
attachment which they bear. 
The most marked differences between the three forms are 
found in the production of Botrytis conidia in the first and its 
absence inthe other two ; in the production of the Peziza stage in 
the last; in the form and size of the sclerotia and the manner of 
their production; and in the general greater development of the 
mycelium and its spread over the soil in the last two types. 
On the basis of these statements the following suppositions 
are possible as to the relations of these forms to one another an 
the real cause or causes of the disease. 
1. The three types are caused by three distinct species of 
fungi which are peculiarly coincident in certain respects. 
2. The three types are caused by three different forms of the 
Same species, which accounts for the coincidences. 
3. Two of the forms belong to the same species while the 
third is distinct but similar in certain respects. 
CULTURES. 
In order to test further these hypotheses a large number of 
special cultures were made which may now be described. The 
specific object of these experiments was to find out, by growing 
the three forms of fungi under various conditions, whether any 
