[Vol. 10 



204 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



culture of the bacillus in which, of course, there were relatively 

 few cells in the spore condition. In the latter case very few 

 colonies appeared after the third day. In a repetition and ampli- 

 fication of this work, the tobacco extract was not employed, and 

 the organism was suspended in concentrations of alcohol, as 

 follows: 10, 20, 40, 00, and 100 per cent, with controls in bouillon 

 and in distilled water. From all those cases in which the spore 

 suspension was employed, a profuse growth was obtained on every 

 streak culture from 10 to 99 per cent alcohol, with apparently 

 no lessening of the intensity of growth as between 1 per cent and 

 99 per cent. In the case of the acetone-treated material, profuse 

 growth was attained at 10, 30, and 60 per cent acetone with some 

 indication of less in1 ense growth in absolute acetone. 



Following the above observations, made the third day, it was 

 determined to make isolation cultures after the tenth day, and 

 these were accordingly arranged and a careful count made as the 

 colonies appeared. There was a progressive diminution in the 

 number of cells alive from the 20 per cent to the 99 per cent 

 alcohol. For that whole interval, however, this decrease amounted 

 to only about nine-tenths of the organisms present in the infusion. 

 There was scarcely any diminution as between 10 per cent acetone 

 and GO per cent, but in absolute acetone the number of organisms 

 was considerably reduced. These data confirm the statement 

 previously made to the effect that the virus of mosaic is less 

 resistant than certain spore forms of the bacteria. This, however, 

 is not surprising, for whatever may be the nature of the virus, 

 many colloids lose to a considerable degree their hydrophilic 



hen 



The 



therefore, is more particularly the nature of the bacterial sp< 

 which permits survival in the high concentrations discussed 

 problem rather apart from our specific investigation. 



EFFECT OF GRINDING ON THE INFECTIVITY OF THE 



TOBACCO VIRUS 



Inasmuch as the thermal tolerance and the resistance toward 

 dehydrating and disinfecting agents, while suggestive, did not 

 seem to set off this virus as possessing properties peculiarly 

 distinctive, it seemed particularly desirable, in view of the size 



