444 ALLARD: MOSAIC DISEASE OF TOBACCO 
sions were that absolute alcohol killed the virus of mosaic, that 
filtered mosaic sap allowed to stand 3 months without preservatives 
retained its virulence. Koning states that he was unable to obtain 
mosaic in Datura Stramonium, Hvyoscyamus niger, Solanum 
tuberosum or Petunia nyctaginifolia with the sap of mosaic tobacco. 
Hunger (27) in 1902 and also in 1904 (40) reported the results 
of his observations and experiments with the mosaic disease in 
Sumatra Heestablished many important facts. Although many 
of his experiments gave somewhat contradictory results under 
different conditions, he found that transplanting several times did 
not necessarily cause the disease to develop, although he was 
inclined to believe that seedlings pulled from dry soil possibly 
contracted the disease more readily than those pulled from wet 
soil. Although Hunger states that topping tobacco plants at 
six weeks of age produced more disease than topping them at 
three weeks of age, he also found that topping 1,200 plants grown 
elsewhere did not produce the disease in a single plant, although 
these plants were topped at various ages. 
Hunger also grew plants from large, medium, and small seed, 
and concluded that medium-sized seed produced the highest per- 
centage of mosaic plants. The large and small seed produced 
about the same percentage of mosaic plants. It is difficult to 
understand why size of seed, however, should bear any relation to 
the occurrence of this disease. 
Hunger found that cuttings from diseased plants, whether 
rooted in soil or grafted upon healthy stocks, remained diseased. 
Many of his healthy cuttings also became diseased. He states 
that the trouble appeared to have no relation to fertilizer treat- 
ment. He was inclined to believe that the occurrence of the 
disease might be associated with extremely hot days and heavy 
rains. 
It is interesting to note that Hunger regarded the mosaic 
disease as a physiological malady. He refused (33) to accept 
Wood’s theory (18), however, that the disease was associated with 
the inhibitory action of oxidase and peroxidase upon diastatic 
action, since he maintained that these oxidizing enzyms did not 
inhibit the conversion of starch into sugar. He also maintained 
that these enzyms could not diffuse, so that plants would not 
be able to take them from the soil through their roots. 
