FURTHER STUDIES OF THE MOSAIC DISEASE OF 



TOBACCO 



By H. A. AxivARD, 



Assistant Physiologist, Tobacco and Plant-Nutrition Investigations, Bureau of Plant 



Industry 



SUSCEPTIBILITY OF PLANTS TO INFECTION THROUGH THE 



TRICHOMES 



The virus of the mosaic disease of tobacco {Nicotiana tabacum) is readily 

 inoculated into the tissues of healthy plants. The disease may be easily 

 communicated by means of a needle through the roots, the stems, or 

 the leaves. It is interesting to note that inoculations are also success- 

 ful when the virus is introduced into susceptible plants through the tri- 

 chomes of the leaves alone. Experiments have shown that a very high 

 percentage of infection may be obtained when the virus is painted or 

 rubbed lightly upon the leaves with a soft brush.^ 



The following experiments (Table I) make this fact plain. Young 

 plants of the Connecticut Broadleaf variety growing in 3-inch pots were 

 used in all tests. 



Table I. — Experiments showing infectivity of the virus when inoculated into the trichomes 



of leaves of tobacco plants 



1 Clinton has observed that the mosaic disease of tobacco is readily communicable to healthy plants by 

 rubbing the virus upon the leaves. (Clinton, C. D. chlorosis of plants ■miH special reference 

 TO CALICO OP TOBACCO, hi Conn. Agr. Exp. Sta. Rpt. 1914, p. 357-424. pl- 25-32. 1915.) 



Journal of Agricultural Research, 

 Washington, D. C. 



Vol. X, No. 12 

 Sept. 17, 1917 

 Key No. G — 120 



(615) 



