1921] 
DUGGAR & KARRER—SIZES OF MOSAIC DISEASE PARTICLES 345 
then applied, a colorless filtrate being obtained with a pressure 
of about .5 atmosphere or more. The agar filtrates were obtained 
in the first instance by covering a Buchner funnel with filter- 
paper and then pouring on and congealing a layer of the agar to 
a depth of about 3 millimeters, being careful also to coat the 
sides of the funnel to a height that would be greater than the 
depth of the juice employed. Suction was then applied as before; 
filtration, however, was extremely slow. In the other case a 
cylindrical porous atmometer tube was partially filled with the 
melted agar, then by revolving the filter in a position almost 
horizontal and subsequently rapidly revolving it on a block of 
ice, as in the preparation of an Esmarch rolled plate, a layer of 
the agar was deposited throughout the length of the cylinder. 
In the case of the diffusion shells these were filled about half 
full with the diseased juice and then immersed to the depth of 
the inner liquid in small beakers of sterile distilled water. These 
were left for a period of 4 days at a temperature of about 18? C. 
in order that slow diffusion might proceed. The utmost care 
was used to prevent contamination of the exterior of any of the 
vessels employed. Inoculation experiments were made from 
each of the above tests, as indicated in the following outline. 
TABLE I 
INFECTION OF TOBACCO PLANTS WITH MOSAIC DISEASE AFTER 
FILTRATION OR DIFFUSION OF THE DISEASED JUICE 
Experiment Nature of filter Source of Number of 
number or diffusion shell infection plants diseased 
1 Spherical atmometer cup Filtrate 10 
2 Control Control (dt. water) 0 
3 1.5% agar layer Filtrate 0 
4 3.0% agar layer Filtrate 0 
5 Parchment shell A Liquid outside of tube 0 
6 Parchment shell A Liquid inside of tube 10 
7 Parchment shell B Liquid outside of tube 0 
8 Parchment shell B Liquid inside of tube 9 
In the above experiments 10 tobacco plants were inoculated 
in each case. These were thrifty young plants of a common 
