685 



This name originated with Adolph Mayer, who in July, 1879, when the 

 disease had occurred to an alarming extent in Holland, received some dis- 

 eased plants from the Society of Agriculture (Department Wijk bij 

 Duurstede) for investigation. He published the results of his experiments 

 in 1885, in a Dutch periodical and in the following year in the "Landwirt- 

 schaftHchen Versuchsstationen"^ According to F. W. T. Hunger^ Van 

 Swieten in 1857 had first called attention to the mosaic character of the 

 variegated leaves of tobacco in the Dutch plantations but in his later studies 

 on the cultivation of tobacco in Cuba, did not mention the disease which then 

 was called "Rost." At present the disease may exist in any country grow- 

 ing tobacco and, accordingly, has received any number of names. Thus 

 Hunger mentions that in Holland it is not only called "Rost" but in places 

 "Bunt" or "Faule." In Germany the name "Mosaikkrankheiten" holds 

 good. In places it passes as "Mauche ;" in France it is called "La Mosaique" 

 or "Nielle" or "Rouille blanche;" in Hungary it is called "Mozaikhetegsege" 

 and the Tartars in southern Russia call it "Bosuch." In Italy it is described 

 under the name "Mai de Mosaico, or "Mai della holla." In America, in 

 the northern states, it is called "Calico" or "the Frcnching disease ;" in the 

 southern states, on the other hand, "Brindle" or "Mongrel disease" The 

 plantations in Java, Borneo and Sumatra also suffer heavily. The Javan- 

 ese call the disease "Poetih" while it is known in Deli by the Chinese name 

 "Peh-sem"^. 



The mosaic disease may at present be considered the most dangerous 

 disease of the tobacco plant. This explains why it has been thoroughly 

 studied recently from several points of view but the results are often con- 

 tradictory. While some investigators, retaining the old theory with great 

 tenacity, wish to find microbes and think they have found them, others 

 defend the theory that an infection disease is present here, the cause of 

 which must be sought in inexpedient enzymatic activity. 



The diversity of opinion is explained partially by the fact that different 

 phenomena have been included under the mosaic disease which do not 

 belong together. On the other hand, however, the disease can actually 

 appear under different forms. 



We follow Delacroix* in describing its symptoms. He distinguishes 

 two stages :^ — i, loss of color; 2, changes in the form of the diseased leaves. 

 In the first group of symptoms, the edge of the leaf shows sharply outlined, 

 various colored spots of a faded green, which shades off into a whitish color 

 but not into a yellow green as in chlorosis; the pale green parts have spots 

 of dark green color, which is even darker than that of the normal leaf. 

 The dift'erences in color become more apparent when the leaf is held 



1 Mayer, Adolf, Die Mosaikkrankheit des Tabaks. Landw. Versuchs&tat. 1886, 

 Vol. XXXII, p. 450. Part III. 



2 Hung-er, F. W., Untersuchung-en und Betrachtungen uber die Mosaikkrank- 

 heit der Tabak.spflanzen. Zeitsch. f. Pflanzenkrankh. 1905, p. 257. 



3 Hunger, loc. cit. 



4 Delacroix, Georges, Recherches sur quelques maladies du Tabac en France. 

 Paris 1906, p. 18. Extrait des Annales de I'lnstitut national agronomique, 2 ser., 

 Vol. V. 



