3R3 
Station zu Wageningen) was first called to this disease in 1879 by the 
transmission of healthy and diseased leaves, with the inquiry: u Was 
mag der Grand sein, dass in den letzten Jahren die Tabakspflanze so 
selir leidet durch den sogenannten Rost?” 
A comparative chemical analysis was first made of healthy and dis¬ 
eased leaves. This showed no lack of N, K, or Ca in the diseased 
leaves. In tobacco culture there is under ordinary conditions no lack 
of P 2 O 5 , because the plants make only moderate demands on this 
substance, and in the culture methods here in vogue an excess is given 
to the soil. Analyses of the earth from tobacco-sick fields also showed 
that there was no deficiency of plant food. Tobacco is known to be 
very greedy for lime, and consequently a sick earth and one not sub¬ 
ject to the disease were compared. The lime content was small in 
both, but not essentially unlike. These determinations, combined with 
the results reached by experienced growers, seemed to show that the 
disease was not due to defective nutrition. 
A search was then made for nematodes in healthy and sick earth. 
Some were found, but only such as live in humus, and no connection 
between them and the disease was established. 
Plants were grown in specially constructed seed beds, with varying 
temperatures, degrees of moisture, and amounts of nitrogen, and their 
behavior after transplanting closely watched. They all developed 
normally, remained healthy, and were very fine at the end of summer, 
but not so large as those grown in the regular way and set out some¬ 
what earlier. The plants were also set out with twisted and iujured 
roots, but this was harmless. All grew into fine plants. 
Plants were also grown at high temperatures in moist air and sud¬ 
denly transported to the field. No disease resulted. 
The hypothesis that crowding and etiolation in the seed bed might 
be a cause of the trouble was also tested and found wanting. In 1881 
the disease was common, and the author had good opportunity to 
study it near Wageningen and Rhenen. Here for the first time it was 
observed that foreign kinds of tobacco escaped the disease entirely, 
while the disease was not completely absent from any of the sorts 
commonly grown. 
In 1882 various experiments were made to determine whether self or 
cross-fertilization played any part. Plants from the seeds of diseased 
plants were also grown. None.of these experiments had any influence 
on the disease. As usual it appeared on land subject to it and did not 
appear in other places. All these results seemed to indicate a disease 
due to parasites. 
The tissues were searched zealously for fungi, animal parasites, etc., 
not only by the author, but also by several of his friends. At first no 
results were obtained. Only one authority thought he found a mycelium 
in the diseased parts of the leaves, u die sich zu einer Septoria oder 
Phoma entwickeln diirften.” It was at this time Dr. Mayer discovered 
