68 MISSOURI BOTANICAL GARDEN. 
Work on the parasitism of Botrytis is still in its infancy 
and many further experiments will be necessary before the 
interrelations with its host are fully understood. My results 
show that we have two stages in the disintegration of the plant 
tissues. There can be no question that some substance is 
secreted by the fungus which kills the plant cells in advance 
of the mycelium. The author disagrees with Smith (49) 
that the poisoning effect is due to oxalic acid, since delicate 
tests for this acid gave only negative results. Even in old 
sugar cultures on which the fungus has been growing for 
several weeks, no oxalic acid was present. Smith reports that 
he found as high as two per cent of the acid under like con- 
ditions. 
The harmful substance may be some organic acid other 
than oxalic, or it may be a toxin of some kind, which, however, 
is not destroyed by heating to 100°C. The writer has found - 
that weak concentrations of malic, tartaric, oxalic, gallic, and 
acetic acids have an action on the lettuce tissues similar to 
that of the mycelial extract. 
From the cultural work I have found that a number of 
enzymes are secreted by the fungus. These enzymes are 
diastase, invertase, cytase and lipase. It was also shown that 
glucosides were broken down and that the fungus was able 
to live on protein derivatives. The Botrytis investigated 
secretes very little cytase and it seems that too much im- 
portance has been attributed to this enzyme. It may be that 
diastase assists the cytase in breaking down the cellulose and 
in digesting the amylodextrin formed. In agreement with 
the other authors, the experiments show a varying ability of 
the conidia to cause direct infection of the host. This ability 
is always directly proportional to the conditions favoring the 
fungus. 
SUMMARY. 
1. The Botrytis cinerea causing the diseases of lettuce, 
peppers and greenhouse plants mentioned, at the Missouri 
Botanical Garden, is the imperfect stage of Sclerotinia 
