The Ohio Naturalist, 
PUBLISHED BY 
The Biological Club of the Ohio State University. 
Volume XIII. 
JUNE, 1913. 
No. 8. 
TABLE OF CONTENTS. 
Melchers— The Mosaic Disease of the Tomato and Belated Plants . 149 
WiLLiAMS-Caryophyllnceae of Ohio. 176 
Humphrey— The Genus Fraxinus in Ohio. . 185 
McLellan— Meeting of the Biological Club.1S8 
THE MOSAIC DISEASE OF THE TOMATO AND RELATED 
PLANTS.* 
Leo E. Melchers. 
Introduction and Historical Summary. 
The mosaic disease or calico of Solanaceous plants seems to be 
one of those pathological problems, which has resisted the efforts 
of the scientist and baffled the most observant layman for the 
last half century. That progress has been made in the study 
of mosaic disease is obvious, but the great problem of its cause 
still remains to be solved. In the review of its literature, it will 
be noticed that contradictory and conflicting results and con¬ 
clusions have been so numerous, in the scientific investigations 
of this problem, that one cannot accept the results uncondition¬ 
ally. In order to summarize the results, conclusions and theories 
of past investigators, and to make the literature pertaining to 
this disease more accessible, the writer has endeavored to pre¬ 
sent a review and bibliography of the essential literature of mosaic 
disease. It is hoped that this will provide a reliable basis for 
future work. 
The first reference to the disease according to Hunger (1905, 
p. 256), was by Swieten (1857), who mentions a disease which 
resembles the mosaic disease of tobacco. This disease was called 
“Rost” or Fleckenkrankheit (Spot disease), terms by which 
mosaic disease was known for some time. In 1885, Adolf Mayer 
investigated this disease on tobacco and in the following year 
published an account of it, naming it “ Mosaic Disease. ” Koning 
(1899, p. 65), states that Dr. van Breda de Haan, called his 
*Contributions from the Botanical Laboratory of Ohio State Univer¬ 
sity. No. 74. 
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