June, 1913.] The Mosaic Disease of the Totnato. 151 



diseased plants. Shaw (1910) believes the Curly Top of sugar 

 beet to be a trouble pathologically and physiologically related 

 to mosaic disease. Allard (1912) believes that Aphids are carriers 

 of mosaic disease. 



Xomcndature. — The names which have been applied to this 

 singular disease, have been many and varied. In America, 

 mosaic disease, cahco, Frenching, mottle-top and chlorosis are 

 terms applied in the Central States; while in the south, brindel 

 or mongrel disease are more common. In Germany one hears 

 of it as Mosaikkrankheit, Mauche, Fleckenkrankheit or Pocken- 

 krankheit; in France la Mosaique, Nielle or Rouille blanche and 

 in Hungary, Mozaik-betegsege. In Italy it is known as Mai 

 del Mosaico or Maldella bolla and in southern Russia the name 

 Bosuch seems to be the most used. Poetih is the name applied 

 in Stunatra, Java and Borneo. Besides these names there are 

 many colloquial expressions in use. Special names applied to 

 Pockenkrankheit are: "Ospa" (Pox) in Russia; ''Rjabucha" 

 (Dot Hke), in Little Russia; "Pestrizi" (Spots) in S. W. Russia. 



Hosts. 



This disease, although originally' described only on tobacco, 

 has in recent years been found on numerous other hosts. Woods 

 (1902) describes it as being produced artificially on the potatoes, 

 Petunias, Violets and poke weed, and Iwanowski (1903) speaks 

 of it as occurring on the beet and kidney bean. Similar troubles 

 have also been found by Suzuki (1902) on the Mulberry, by 

 Selby (1904) on cucumbers, by Clinton (1910) on lima and string 

 beans, muskmelon and squash. Some investigators would place 

 mosaic disease in the same class with albinism or variegation; 

 (Woods 1S99). Orton reported it on potatoes at the Cleveland 

 meeting of the American Phytopathological Society, 1912^13, 

 and the writer has recently found it occurring naturalh^ on the 

 potato in the greenhouse. 



Characteristics. 



Tobacco. — As already indicated above, this malady seems to be 

 present throughout the tobacco growing regions of the world, 

 although there are some countries growing tobacco extensively 

 from which no reports of its occurrence have been seen. 



This disease usually makes its first appearance either in the 

 seed-bed or cold-frame. The middle or lower leaves are the first 

 attacked and gradually the uppennost leaves show the character- 

 istic symptoms. The disease reveals itself on the leaves by an 

 irregular, more or less mottled effect, a differentiation into yel- 

 lowish and dark green areas. The dark green areas are often 

 confined quite largely to a border along the larger veins, while 

 the intermediate tissue assumes a lighter green or yellowish hue. 

 Upon closer inspection differences may be noticed; the adjoining 



