174 



Journal of Agricultural Research voi. xxn. N0.3 



casual agents in the transmission of mosaic and leafroll of Irish potato.^ 

 In view of these field observations experiments on this disease were 

 conducted in the greenhouse at Washington, D. C, during the winters of 

 1919-20 and 1920-21. 



TRANSMLSvSION WITH PLANT JUICE 



Chinese cabbage, mustard, and turnip plants showing mosaic mottling 

 were taken from the field and planted in pots in the greenhouse. Only 

 a small percentage of these mature and mosaic plants survived trans- 

 planting, so that the supply of mosaic material for inoculations was thus 

 considerably reduced, and therefore only a small number of healthy 

 plants were inoculated at one time. 



Inoculations with juice were made by rubbing the leaves between the 

 fingers so that considerable sections of the leaflets were crushed, apparently 

 permitting the applied juice to be absorbed by such areas of the leaf as 

 still remained free or partly free from mutilation. Such operations were 

 performed chiefly upon the youngest leaves, the first applications being 

 made when the plants had developed about five leaves. In Table I the 

 results of these inoculations are presented. 



Table I. — Inoculations with juice from mosaic plants 



Variety and species 

 inoculated. 



Time of inocu- 

 lation. 



Source of juice. 



Southern 



turnip. 



Do. . 



Do. . 



Prize 



Mustard . 

 Do. 



Do. 

 Do. 



Pe-tsai or Chinese 

 cabbage. 



Do 



Do 



Dec. 4, 1919 . 



do 



Dec. 6, 1919 . 



...do 



/Mar. 8, 192 1 



\Mar. 21, 192 1 



fMar. 9, 192 1 



\Mar. 21, 1921 



Jan. 15,1921 



Dec. 4, 1919 



....do 



Dec. 6, 1919 



Mosaic Southern 



Prize tiu-nip. 

 Healthy turnip. . . . 

 Mosaic Green Moun- 

 tain potato. 

 do 



}....do 



[Mosaic mustard. . . . 



Mosaic pe-tsai or 



Chinese cabbage. 



do 



Healthy 



Mosaic Green Moun- 

 tain potato. 



Per cent- 

 age mosaic. 



67 



63 

 60 



1^ 



<» Date of last observation April 2, 1920 and 1921. 



The data indicated in Table I disclose the fact that mosaic mottling 

 was obtained only when juice from a mosaic plant was introduced into 



I ScHULTz, E. S., FoLSOM, Donald, Hildebrandt, F. Merrill, and Hawkins, Lon A. investigations 

 ON THE MOSAIC DISEASE OF THE IRISH POTATO. In Jour. AgT. Research, v. 17, no. 6, p. 247-274, pi. A-B 

 (col.), 25-30. 1919. Literature cited, p. 272-273. 



ScHULTz, E. S., and Folsom, Donald, transmission of the mosaic disease of irish potatoes. In 

 Jour Agr. Research, v. 19, no. 7, p. 3x5-338, pi. 49-56. 1920. 



ScHULTZ, E. S., and Folsom, Donald, leafroll, net-necrosis, and spindling-sprout of the irish 

 POTATO. In Jour. Agr. Research, v. 21, no. i, p. 47-So, pi. 1-13 1921. Literature cited, p. 7S-80. 



