Dec. it, 1916 Specific Mosaic Disease in Nicotiana viscosum 
485 
Jimson weed, however, sometimes shows 
considerable resistance to the mosaic dis¬ 
ease affecting N. tabacum . 
(12) Highly infectious and particularly 
malignant to N. rustica. 
by the ordinary mosaic disease of 
tobacco. 
(12) All attempts to infect N. rustica 
have been unsuccessful. 
The writer is of the opinion that this distinctive type of mosaic disease 
affecting N. viscosum has in some manner originated from the ordinary 
form of mosaic disease, possibly through the agency of insect transmission 
in the field. This does not seem improbable, since practically every sus¬ 
ceptible plant in a half-acre field of* ordinary tobacco in which the N.. 
viscosum plants were grown became mosaic; and throughout the season 
both species were infested with great numbers of flea beetles. It is 
possible that insects may become efficient transmitters of disease where 
ordinary methods of artificial inoculation fail. 
During the same season the writer's attention was called to the occur¬ 
rence of typical symptoms of the mosaic disease in peppers grown in a 
field near by. To all outward appearances the plants were affected with 
a severe mosaic disease which gradually spread over the field and per¬ 
sisted in all affected plants. Tomato plants in adjoining rows, however, 
were unaffected. The expressed sap from the most severely attacked 
pepper plants failed to produce the mosaic disease in young tobacco 
plants (N. tabacum). Whether this mosaic disease was infectious to 
healthy pepper plants or might have been in any way related to the 
mosaic disease affecting N . viscosum was not determined. 
In this connection it is interesting to note that various European in¬ 
vestigators have reported that they were unable to inoculate other 
species of solanaceous plants with the virus of the mosaic disease of 
tobacco with which they worked. Thus, Mayer 1 failed to produce the 
disease in other solanaceous plants. 
Iwanowski 2 has stated that the mosaic disease of tobacco does not 
occur upon Datura stramonium or Hyoscyamus niger . 
Iwanowski, 3 in a later publication, stated that he had never known 
Nicotiana rustica to be affected by the mosaic disease. 
Koning 4 also failed to communicate the mosaic disease of tobacco to 
Datura stramonium , Hyoscyamus niger , Solanum tuberosum , and Petunia 
nyctaginifolia. 
Westerdijk, 5 working with a mosaic disease which was infectious to 
tomatoes, reported that she could not communicate this disease to 
1 Mayer, Adolf. Ueber die Mosaikkrankheit des Tabaks. In Landw. Vers. Stat., Bd. 32, p. 450-467, 
pi. 3. 1886. 
2 Iwanowski, D, fiber die Mosaikkrankheit der Tabakspflanze. In Bui. Acad. Imp. Sci. St. Petersb., 
n. s. v. 3 (v. 35)1 *10.1. P- 67-70. 1892. 
3 Iwanowski, D. fiber die Mosaikkrankheit der Tabakspflanze. In Centbl. Bakt. [etc.] Abt. 2, Bd. 5, 
No. 8, p. 250^254, 2 fig. 1899- 
4 Koning, C. J. Der Tabak ... p. 71-86, fig. 13-15. Amsterdam, 1900. 
3 Westerdijk, Johanna. Die Mosaikkrankheit der Tomaten. 19 p., 3. pi. Amsterdam, 1910. [Meded. 
Phytopath. Lab. ** Wille Commelin Scholten.” Amsterdam.] 
