A PARASITIC BOTRYTIS ON PEPPER AND LETTUCE, 67 
ber of organic acids, or it may be that the fungus secretes 
some other toxic substance which causes the death of the 
cells. 
DISCUSSION. 
There can be no question but that the disease on the 
peppers, lettuce and other plants in the greenhouses of the 
Missouri Botanical Garden was caused by Botrytis cinerea, 
which possessed the power of penetrating the plant tissues and 
destroying them. 
The lettuce “drop” due to Botrytis cinerea has about the 
same characteristic symptoms as when caused by Sclerotinia 
Libertiana. It is, indeed, interesting to note the similarity 
between the symptoms of the disease described by Stevens and 
those noted by the writer. Even the physiology of the two 
fungi agree to a large extent. The difference, of course, is 
that Botrytis produces only conidia, whereas S. Liber- 
tiana only ascospores. In this connection I might say that I 
have been able to develop from Botrytis a mycelium that does 
not produce conidia. From my observations it appears that 
the more parasitic the Botrytis becomes, the greater is the 
number of sclerotia and the fewer the conidia produced. 
That Botrytis can become a serious disease was very well 
shown in the greenhouse the past winter. To become 
parasitic, however, it must have suitable conditions. The life 
cycle of the fungus is complete with the germination of the 
sclerotia, resulting in the production of conidiophores. This 
appears to be the prevailing type of sclerotium germination. 
Istvanffi (28) is the only one who in recent years has been 
able to obtain ascospores from sclerotia of Botrytis. Since he 
was unable to produce infection by means of the ascospores, 
he failed to complete the life cycle of the fungus. Apothecia 
were rare ; the sclerotia formed conidiophores more commonly. 
It may be safely stated, then, that the Botrytis causing lettuce 
“drop” and similar diseases is a degenerate form which has 
lost the apothecial stage. 
