ALLARD: MOSAIC DISEASE OF TOBACCO 445 
Hunger (36) also, in 1903, reported the results of various ob- 
servations and experiments made in Deli, Sumatra, to determine 
how the mosaic disease was spread in a tobacco field. He showed 
that coolies in the operation of searching for caterpillars readily 
communicated the disease from diseased to healthy plants through- 
out the field. He stated that by touching a diseased plant first 
and then healthy plants ‘‘all touched plants without exception 
became diseased.” He concludes that careless, inexperienced, and 
short-sighted coolies are largely responsible for the spread of the 
disease in a field. In this respect he confirmed the topping experi- 
ments reported previously by Koning (15). 
Hunger again published, in 1903 (35), an interesting paper 
showing that the spread of mosaic in the Deli, Sumatra, fields is 
very largely due to coolies employed to search for tobacco worms. 
Very careful experiments were made with plats and rows, in such 
a way that a mosaic plant was the first plant touched. Beginning 
with this, only alternate plants, 3, 5, 7, 9, etc., were searched for 
worms. The plants represented by the even numbers were in- 
tended for controls and remained untouched. In all instances, 
practically every plant in the series beginning with the mosaic 
plant sooner: or later became mosaic. At the same time, the 
controls, with few exceptions, remained healthy. 
Hunger states that the less experienced coolies often become 
notorious as mosaic carriers. Coolies with this reputation are 
frequently troubled with defective vision as well. In the opera- 
tion of worming, such coolies find it necessary to pause before 
each plant to determine if worms are present, and in the search 
the young, central leaves are handled more or less. On the other 
hand, the skilled, keen-eyed coolies pass rapidly from plant to 
plant without finding it necessary to touch the leaves in order to 
learn if a worm is present. Should a worm be seen it is skillfully 
removed. Mosaic infection under such conditions is reduced to 
the minimum through the operation of worming. 
An instance is given of two coolies, who, from year to year, 
spread mosaic in all the fields they wormed. A medical examina- 
tion indicated that both were very near-sighted. 
Hunger (41), in 1904, also published the results of his experi- 
ments with the retransplanting of tobacco plants, before finally 
