June, 1913.] The Mosaic Disease of the Tomato. 
165 
But he states that there is evidence that rapid growth, caused 
by excessive nitrogenous manure or too high a temperature, is 
favorable to it. This latter statement seems to correspond with 
observations made by the writer on the appearance of some 
cases of tomato mosaic under glass. Woods (1902), does not 
explain why nitrogenous fertilizers should act in this manner; 
the plants are really in need of reserve nitrogenous compounds, 
as will be seen later. He says, however, (p 23), “It is probably 
connected, however, with the manufacture of reserve nitrogen 
by the cells and its distribution to the rapidly growing parts. ” 
He thinks that tobacco mosaic is especially liable when moist 
cloudy weather, stimulating rapid growth, is followed by hot, dry 
weather, checking growth and causing the soil to bake, so that 
cultivation is apt to injure the root system. 
He carried out inoculation experiments along the same lines 
as other investigators, showing that this disease is infectious. 
He performed other experiments however, to prove that mosaic 
disease could be produced at will without employing the juice 
of diseased or healthy plants. He w r as able to produce mosaic 
disease on tomato plants by severally pruning them. Pot-bound 
tobacco plants were selected and after they had been cut back, 
(allowing two or three lower leaves to remain), they were sub¬ 
mitted to high temperature and copious watering. The rapidly 
developing shoots became mottled and often distorted. Mosaic 
disease appeared in plants which were simply punctured with 
a steril scalped and in other cases w r here a piece of healthy leaf 
was inserted. Juice of diseased plants, boiled and double boiled 
when injected into the terminal bud, or poured around the roots 
caused the appearance of the disease, Woods (1899, p. 753) 
says, “It seems plausible that in rapid, poorly nourished growth 
many of the cells were unable to develop their normal amount 
of chlorophyll by reason of the excessive development of oxidizing 
enzymes. ” 
Oxidizing Enzymes .—Woods states (1902, p. 23), “The disease 
is not due to parasites of any kind, but is the result of defective 
nutrition of the young dividing and rapidly growing cells, due to a 
lack of elaborated nitrogenous reserve food accompanied by an 
abnormal increase in activity of oxidizing enzyme in the diseased 
cells.” According to Woods (1902), this excess of oxidases in 
turn inhibits diastatic activity so that starch accumulates in 
diseased cells in abnormal quantities. The resulting imperfect 
translocation may be demonstrated by the application of iodine 
at different hours during a day. By this means a striking difference 
between the normal and the abnormal tissue may be demon¬ 
strated. Suzuki (1902) arrives at similar conclusions, in the study 
of his mulberry disease; he confirmed Woods’ experiments, showing 
that it was brought on by excessive pruning and that there was an 
