June, 1913.] The Mosaic Disease of the Tomato. 159 



and 26 from apparently normal fruit from diseased plants. All 

 this second generation showed an intensive leaf reduction; the 

 yellow spots appeared entirely inconspicuous. Variegated ex- 

 amples did not occur. The plants grown in the garden showed 

 abnormal appearances all at the same age. Leaf reduction 

 was less noticeable, although leaf apexes and side shoots were 

 somewhat abnormally developed. A pronounced case of disease 

 did not occur. In the greenhouse, the plants showed indefinite 

 cases of mosaic disease. One plant out of 27 had strong symptoms 

 of leaf reduction. She states (p. 17), "By the field experiments 

 it has been shown without a doubt that the disease is inheritable. 

 Also here it is shown that the light factor is important in develop- 

 ing the disease. " 



Resistance and Selection. — Hunger (1905) believes through 

 proper selection a resistant strain of tobacco can be obtained, 

 (p. 297). "On page 282 it was shown how diversely plants 

 may develop from Deli seed, even when of the same variety, 

 and I am convinced that it is possible, through proper selection 

 of such seed to isolate and obtain constant physiological strains 

 whose peculiarities would remain fixed within certain limits of 

 temperature." Bouygeres and Perreau (1904) claim to have 

 reduced mosaic disease 98% in a season by selecting seed from 

 a plant which remained healthy among a diseased lot. 



Various Names for Same Disease. 



Considerable confusion and dispute exists among European 

 investigators, as to whether Pockenkrankheit, Fleckenkranl-cheit 

 (Spot disease) and mosaic disease, are the same or different. 

 Mayer (1886) describes the Mosaikkrankheit, in its second stage 

 by saying that the yellow areas gradually become brown and 

 eventually dry up. These are also the views held by Prillieux 

 and Delacroix (1894); and Marchal, Gontiere and Bouygues 

 (according to Hunger 1905). This stage corresponds to the 

 disease described as Pockenkrankheit by Iwanowski (1892) (b), 

 who noticed it in 1888, and on account of the differences in ap- 

 pearance gave it the distinctive name, "Pockenkrankheit," 

 (Pox Spot). He says (p. 68), "The Mosaic disease is contagious, 

 but such is not the case with Pockenkrankheit. The condition 

 producing Pockenkrankheit is excessive transpiration. " He 

 criticises (1902) Beyerinck, Koning and Heintzel for considering 

 Pockenkrankheit and mosaic disease the same trouble. On the 

 other hand, Delacroix (1905) assigns the name "rouille blanche," 

 to a spotting of tobacco caused by a specific bacterium. He says 

 "rouille blanche" must be limited to the so-called Pockenkrank- 

 heit, as named by Iwanowski. Westerdijk (1910) states that 

 Pockenkrankheit (" necrobiotische form"), does not occur on 

 the tomato, but that it is very common on tobacco; even more 



