The Ohio 'iJ^aturalist, 



PUBLISHED BY 



The Biological Club of the Ohio State Uni'versiiy, 

 Volume XIII. JUNE, 1913. No. 8. 



TABLE OF CONTENTS. 



Melchers— The Mosaic Disease of the Timiato and Eehxted Plants 149 



WiLLiAMS-Caryophyllaeeae 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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