[Vor. 4 
216 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
data show that oxidase activity was also destroyed at this 
point. A temperature of —180° C. did not destroy the 
*virus." Although some organisms can withstand a tempera- 
ture as low as this, it is also a fact that chemical compounds, 
including enzymes, can be cooled to any degree without 
changing their constitution. 
Various workers have found that fermented extracts of 
mosaic material gradually lose their infectious properties. 
This has also been experienced by the writer. Allard (716%), 
on the other hand, states ‘‘that the virus will retain its in- 
fectious properties almost indefinitely without the addition 
of toluene. With no preservative whatever added, the bottled 
virus was highly infectious when tested 12 to 15 months later, 
although putrefaction had taken place.” We are not in a 
position to discuss this matter at this time since we are abso- 
lutely ignorant of the cause of this putrefaction. It might 
have been due to the action of bacteria, of wild yeasts or 
fungi, or the activity of autolytie enzymes present in the ex- 
tract. On the other hand, if the infective principle is as sensi- 
tive to formaldehyde as Allard’s results indicate, the destruc- 
tion of the infectious properties might have been due to the 
formaldehyde resulting from the oxidative decomposition of 
chlorophyll (Warner, 74). Тһе extracts are preserved as 
aqueous solution, generally using toluene as a preservative. 
This is exactly the manner in which enzyme digestion mix- 
tures are set up, which is further indication that when putting 
up an extract of mosaic material in this manner, we are pre- 
serving an enzyme and not an organism. 
Considerable disagreement may be noticed in the literature 
as regards the transmissibility of the mosaic disease of 
certain plants to other species. Some of the work on this 
phase of the problem is reviewed briefly in a recent article 
by Allard (716"), and results are reported which indicate that 
the mosaic disease of Nicotiana viscosum is distinct from 
that of Nicotiana tabacum. These results might lead one to 
conclude that these are ‘‘biological species’ or ‘‘physio- 
logical races’’ of the mosaic **virus." However, it is a well- 
known fact, particularly in animal physiology, that fluids, 
