THE MOSAIC DISEASE OF TOBACCO. 9 



away the main stalk, showing only the mottled corollas. Two large, 

 vigorous, apparently healthy lateral suckers several feet in length 

 were left undisturbed, and in three days these also had developed all 

 the symptoms typical of the disease. 



Local manifestations of the disease were readily induced in a 

 number of mature plants by inoculating the apex of a tall, vigorous 

 sucker. The earliest symptoms were frequently confined to the- 

 branch inoculated and usually first appeared in the small secondary 

 suckers nearest the point of inoculation. Plate IV, figure 2, illustrates 

 a typical instance of this sort. A tall plant of the Sumatra variety 

 was allowed to blossom, and it soon developed suckers freely. As 

 shown in the illustration, some of these were nearly as long as the 

 main stalk. On February 9 one of these (at A) was inoculated 

 thoroughly in the immature flower head (when only one- fourth inch 

 across) and at the first bald sucker just below. At this time the 

 flower head B of the main stalk had been in bloom several weeks 

 and all the blossoms produced were of a uniform pink color. The 

 branch or sucker (at C) had not yet blossomed. On February 21 

 the first symptoms of the disease appeared in the inoculated branch 

 A, the blossoms of which were pale white or conspicuously mottled. 

 Likewise, the small axillary shoots (at a and b) were just showing 

 mosaic symptoms. No other indications of the disease were notice- 

 able in the plant. Examined again on March 4 the blossoms of the 

 branch A were distinctly mottled, although those of the main flower 

 head B and the branch G were still normal in color. On March 5 a 

 large immature basal sucker was showing mosaic symptoms, and on 

 March 25 this basal sucker was producing leaves and blossoms mot- 

 tled to a very pronounced degree. The main stalk B and the branch 

 C did not at any time show symptoms of the disease, either in the 

 small axillary suckers or in the color of the blossoms. 



Although local mosaic symptoms may sometimes develop as the 

 result of certain methods of inoculation, the disease invariably 

 becomes general, appearing in other immature growing parts of 

 affected plants. In all respects this progressive development of 

 mosaic is strikingly similar to the behavior of peach yellows, as 

 described by Smith. 1 He says: 



There is also a progressive development of the disease, more and more of the 

 tree becoming involved. In other words, it appears first to be a local disease; 

 then, later on, a general one. Quite often, the first season, only one limb or a few 

 limbs are diseased, but additional limbs are invariably affected the second year. 

 I know of no exception to this. The first year of attack it is comparatively 

 infrequent to find a tree diseased in all its parts; the second year it is some- 

 what rare to find many sound branches ; often there are none. 



1 Smith, Erwin F. Peach yellows, a preliminary report. U. S. Department of Agri- 

 culture, Botanical Division, Section of Vegetable Pathology, Bulletin 9, p. 91, 



13128°— Bull. 40—14 2 



