650 



Journal of Agricultural Research 



Vol. VI, No. 17 



way. The writer has been unable to obtain the finer pored Berkefeld or 

 Pasteur-Chamberland bougies of the same type because of the European 

 war. By using the Livingstone atmometer porous cup, however, a 

 method of filtration has been devised which has given very interesting 

 results. The construction of this apparatus is shown in Plate XCI. The 

 extracted sap is first filtered thiough filter paper to remove all suspended 

 material. The clear dark-amber solution is then filtered through the 

 porous cup under reduced pressure (approximately 3 inches of mercury). 

 After passing through the atmometer, the virus has completely lost its 

 infectious properties, yet an intense peroxidase reaction is given with 

 guaiac and hydrogen peroxid. 1 



Table I. — Infectivity of the mosaic virus after it has been filtered through the Living- 

 stone atmometer porous cup in IQ15, 10 Connecticut Broadleaf plants having been used 

 in each test 



FILTRATION THROUGH POWDERED TALC 



Numerous experiments have shown that the infective principle of the 

 mosaic disease of tobacco may be completely removed by filtering the 

 virus through powdered talc. 



In these experiments (Table II) Hirsch's porcelain funnel, having a 

 diameter of 9 to 10 cm. and furnished with a stationary perforated disk, 

 was used. A disk of hard filter paper was placed over this disk to retain 



1 Woods used the guaiac and guaiac hydrogen-peroxid tests giving the blue coloration for the determina- 

 tion of oxidases and peroxidases in the extracted sap of tobacco plants. Since the oxidase theory as ex- 

 pressed by Woods was based upon results secured with these tests, the same tests were used in the writer's 

 experiments. The terms "intense," "strong," "weak," etc., have been used to designate the relative 

 intensity of the blue coloration. An " intense" peroxidase reaction is one giving at once an intense indigo 

 blue. The term "strong" indicates that the blue coloration is not as deep, and appears more slowly. The 

 term "weak" denotes a light-blue coloration. 



