June, 1913.] The Mosaic Disease of the Tomato. 
i5 1 
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. 
Nomenclature .—The names which have been applied to this 
singular disease, have been many and varied. In America, 
mosaic disease, calico, Frenehing, 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 Sumatra, Java and Borneo. Besides these names there are 
many colloquial expressions in use. Special names applied to 
Pockenkrankhcit are: “Ospa” (Pox) in Russia; “Rjabucha” 
(Dot like), 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 naturally 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 uppermost 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 
