[Vol. 10 



206 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



was taken after each interval, the sample being removed from 

 directly beneath the pestle. This was placed in a sterile weighing 

 flask and weighed. One-tenth gm. of the sample was diluted to 

 9 cc, giving a dilution of 1 :100. From this, other dilutions up 

 to 1 to 10 6 were made, and poured plates were arranged from these 

 dilutions. A sample from the original bouillon culture mixed 

 in the same proportion with the diatomaceous earth, without 



grinding, wa 



made 



d out at similar concentrations. Duplicate 

 in every case. The result of these experiments 

 indicated that even after grinding the spores of Bacillus subtilis 

 for only 3 hours very few remained viable, an average of 32 per 

 culture at a dilution of 1 :100, at which dilution the control showed 

 innumerable colonies. After 6 hours of grinding the viable spores 

 averaged 2 per culture, and no greater dilution yielded any colonies 

 whatsoever. After 9 hours a single colony appeared at a dilution 

 of 1:100, and no colonies at greater dilutions. Grinding was 

 therefore thoroughly efficient in killing the spores of bacteria. 

 We have carried out a variety of experiments on temperature 

 relations, the effects of disinfectants, the action of light, etc., 



of the mosaic 



indicate 

 the mos 



wise failed thus far to give any evidence of change in the culture 

 solutions indicative of the activity of living organisms. In 

 addition to these lines of research we have also undertaken ex- 

 tensive experiments, beginning in the winter of 1921-22, in the 

 filtration of bacteria, with the idea of determining the capacity 

 of such organisms to pass filters when apparently the spore or cell 

 sizes were greater than the diameters of the pores, or lacunae, of 

 the filters employed. These experiments have yielded results 

 of striking interest, and in time they will be published separately. 



b 



possible, both because of the 



mosaic 



' ' am 1 



dimensions 



In endeavoring to arrive at something more concrete than the 

 name "virus" to explain the general nature of the mosaic 



mere 



disease agency, we need to recall many facts bearing upon some- 

 what related phenomena. From the investigations of Lindstrom 



