THE MOSAIC DISEASE OF TOBACCO. 19 



Eight plants were inoculated with the sap of the roots of a diseased plant. 

 Nine plants were inoculated with the sap of a healthy plant. 



When examined 16 days later 8 out of 9 plants in the series inocu- 

 lated with the mosaic topmost leaves of the diseased plant were badly- 

 diseased. Of the 8 plants inoculated with the sap of the appar- 

 ently healthy lowermost leaves of this plant, 5 had also developed the 

 disease. Of the 8 plants inoculated with the juice of the roots, 6 

 plants had become diseased. The 9 controls treated with the juice 

 of a healthy plant remained healthy. 



Inoculations made with the juice of corollas of mosaic plants were 

 carried out in the following manner: Three series of 9 plants each 

 were arranged -for the experiment. These plants were grown in 

 4-inch pots and were of the same age, size, and variety as those used 

 in the two preceding tests. The plants of each series were inoculated 

 alike on June 11 by puncturing two or three leaf blades. 



Nine plants were inoculated with the sap of mosaic leaves of a diseased 



plant. 

 Nine plants were inoculated with the sap of the corollas of this same plant. 

 Nine plants were inoculated with the sap of a healthy plant, as a control. 



In 11 days (June 22) all of the 9 plants inoculated with juice 

 expressed from corollas of the mosaic plant had become diseased; 

 likewise all of the 9 plants of the series treated with the mosaic 

 leaves of this same plant were diseased, but the 9 controls receiving 

 the healthy juice remained healthy. 



Similar results were again obtained in a second experiment. On 

 March 28, 20 young Sumatra plants growing in small pots were ar- 

 ranged in two rows of 10 each. One series of 10 plants was inoculated 

 with the expressed juice of corollas of a mosaic jDlant; the second 

 group of 10, serving as controls, was inoculated in the same manner 

 with the expressed juice of corollas of a healthy plant. On April 15, 

 6 of the 10 plants receiving the sap from corollas of a mosaic plant 

 had developed the malady. The 10 controls remained free from dis- 

 ease. 



Various similar experiments have always confirmed these results. 

 It is evident at once that an active infectious principle resides in all 

 parts of mosaic plants, although such plants frequently indicate only 

 local symptoms of the disease. 



DISSEMINATION OF VIRUS FROM THE POINT OF INOCULATION. 



If the mosaic virus is pricked into a leaf of a healthy tobacco plant, 

 an infectious principle disseminates itself from this point into all 

 parts of the plant. The following experiment gives some idea of the 

 rate of dissemination of the virus from the point of inoculation : 



Seventy young, vigorous Connecticut Broadleaf plants growing in 

 pots were arranged in 7 rows of 10 plants each. On March 28, 1912, 



