1917] 
FREIBERG—MOSAIC DISEASES 213 
this were then used for inoculations. The precipitates ob- 
tained with 45 and 50 per cent alcohol produced the disease, 
while those obtained with 75 and 80 per cent alcohol gave 
negative results. Any one familiar with the preparation of 
enzymes is conscious of the fact that the higher concentra- 
tions of alcohol destroy most enzymes in a comparatively 
Short time, and this is probably what happened when Allard 
treated his material with alcohol for 2 days. Dilute concen- 
trations of alcohol do not exert a deleterious action, and 20 
to 30 per cent is therefore often used during the process of 
extraction in order to prevent bacterial action. The results 
of Allard should, therefore, not be interpreted as proof of 
the destruction of the mosaic organism by higher concentra- 
tions of alcohol, but rather to illustrate the deleterious effect 
which high concentrations of alcohol exert on enzymes such 
as the infective principle of.mosaie diseases. 
Extracts were next treated with hydrogen peroxide in 
order to destroy the oxidases. A concentration was found at 
which all oxidases were destroyed, but the infective principle 
was retained. It was this method which enabled Allard to 
demonstrate that mosaic diseases are not caused by oxidases. 
The problem was then attacked from the other angle and the 
infective principle was destroyed while the oxidases were 
retained. This was accomplished by adding different concen- 
trations of formaldehyde. When concentrations of formalde- 
hyde of 1:800 and 1:1000 were employed, only 1 plant out of 
10 became infected. When greater concentrations were used 
no infections resulted, while with greater dilutions the infec- 
tious properties were retained to a considerable degree. Al- 
though not specifically stated by Allard, this was presumably 
interpreted to mean that formaldehyde was penetrating 
enough to kill the organism. On the other hand, it suggests 
a specificity of reaction of a compound with formaldehyde, 
and probably with aldehydes in general. Furthermore, if 
formaldehyde is one of the first products of photosynthesis, 
as contended by Usher and Priestley (’06, ’06"), Schryver 
(710), and others, one can easily conceive of a physiological 
origin of mosaic diseases. There is less carbohydrate in the 
