436 ALLARD: MOosAIC DISEASE OF TOBACCO 
krankheit.”” Likewise Koning, Heintzel, and Beijerinck failed 
to distinguish clearly between the two diseases. The published 
accounts of Prillieux and Delacroix, Marchal, Goutiére, Perreau, 
and Bouygues indicate that in many instances these investigators 
had confined their attention entirely to ‘“‘Pockenkrankheit”’ or 
some other leaf-spot disease. This failure to distinguish the true 
mosaic disease from various other pathological troubles finally 
led to considerable confusion as to the bacterial nature of the 
trouble supposed to be the true infectious mosaic disease described 
by Mayer. 
Dr: Adolf Mayer (2), Director of the Experiment Station at 
Wageningen, Holland, appears to have given in 1886 the first 
scientific account of the mosaic disease of tobacco, terming it 
‘“‘Mosaikkrankheit,’”* whence the common term ‘mosaic’ for 
this disease. Although Mayer failed to distinguish between this 
disease and “‘ Pockenkrankheit,” his accurate description of various 
facts and symptoms of the disease with which he worked identifies 
the first phase without question as the true mosaic disease affecting 
American tobacco. The more important facts brought out by 
Mayer may be briefly stated as follows: 
He first proved that the disease was communicable by artificial 
inoculation; that the sap of healthy plants was not infectious; that 
an incubation period of 10 or 12 days preceded the first observable 
symptoms; that the disease was persistent, appearing ultimately 
in all immature growing parts of affected plants; that diseased sap 
filtered once through filter paper still retained its virulence; that 
sap sufficiently heated lost its virulence: and that the seed of 
affected plants did not carry the disease to the next generation. 
Mayer failed to produce the disease in other solanaceous plants. 
Further, he found that liming, crowding the plants, sudden atmos- 
+ According to Finer. J. H. Swieten, as a result of bese oe of a disease 
of tobacco in the Opper-Betuwe, possibly gave the first acc t of mosaic in 1857- 
Among the tobacco growers the disease was known as peng a term at the present 
time usually applied to the mosaic dise 
the year 1866 Swieten spent pair months in Cuba in connection with aa 
lems relating to tobacco culture, but did not mention the mosaic disease as occur rin, 
See De tabaksteelt te Elst en omstreken in de Opper-Betuwe. Tijdschr i 
ter bevordering van Nijverheid, 1857, tweede reeks, Deel 5, pp. 147-167, and Besch- 
rijving van te teelt en bereiding van de Cuba-tabak. Tijdschrift voor Nijverheid en 
Landbouw in Ned-Indie, 1866. Deel XII, pp. 23 mea 
