16o 
The Ohio Naturalist. 
[Vol. XIII, No. 8, 
so than the “yellow-green mosaic” which is scarcely known to 
many tobacco growers. Sturgis (1899, p. 258) states, “It is 
evident that in this so-called “spotted disease” of tobacco, we 
have a disease very similar to, if not identical with, that known 
in Connecticut as “spotting” and furthermore, that this disease 
is as distinct from mosaic of foreign tobacco as “spotting” is 
from “calico.” If the statements of the Russian investigators 
above mentioned are correct (and there is every reason for so 
regarding them), “spotting” is probably due to excessive trans¬ 
piration induced by sudden atmospheric changes.” In regard 
to “spotting,” in this country, he says (1899, p. 254, “It is a 
peculiar disease, not very common, not confined to any one locality 
and not characteristic of any special soil. As I have seen it— 
it is signalized by the presence on the leaf of small circular spots. 
These usually occur in the greatest numbers at or near the tips of 
the leaves, at first— yellow in color—irregular in outline—. The 
tissue within the border finally dies and becomes almost white, 
but except in severe cases, it does not break away from the leaf. ” 
He goes on to say that microscopic examinations have never 
shown the presence of fungi or bacteria. “Nothing further, 
therefore, can be said regarding this trouble, nor would it have 
been considered worthy of mention were it not for its resemblance 
to a disease of tobacco which occurs in Europe and Asia. ” Woods 
(1902) does not seem to mention this trouble. 
There is no serious confusion in this country regarding 
these troubles; they seem to be distinguishable. According to 
Sturgis (1900), the “spotting” which may occur at times is not 
undesirable to a limited extent, as it enhances the value of to¬ 
bacco. It is sometimes artificially produced by spraying with 
certain chemicals. 
Causes of Mosaic Disease. 
The causes which have been assigned to this disease are 
numerous and varied. A great many have been recklessly 
assigned, as often is the case when some undetermined disease 
has long resisted the efforts of investigators. According to Hunger 
(1905) it is still believed by many growers in Europe that “bad 
intentions” on the part of some one had much to do with its 
appearance. In Deli it was claimed that the disease appeared 
where the Coolies had urinated on the plants in the hot-bed, 
while in other cases laborers were accused of possessing the 
“warm hand.” 
Among recent students the cause of mosaic disease is generally 
considered to be due either (1) To bacterial infection, (2) The 
Virus theory, (3) A physiological disturbance. 
1. The Bacterial Theory .—Here a specific organism, a bac¬ 
terium, is stated to be the cause of mosaic disease. The supporters 
