KUNKEL: VIRUSES 95 



injured. Peach yellows (6), aster yellows (7), and witches' broom of potato 

 can be cured by heat in certain of the plants they affect. The false blossom 

 disease also can be cured (8). When plants are cured, all of the bizarre effects 

 produced by the viruses causing these diseases disappear. Cured peach trees 

 become dormant when the season for dormancy arrives. Cured potato plants 

 live no longer than healthy plants. The stimulating and stunting effects of cran- 

 berry false blossom virus in periwinkles subside and disappear when the plants 

 are cured. It is apparent that these viruses affect growth only during the period 

 in which they are present in the plants. The malformations that develop while 

 plants are sick are of course not corrected by cure, but all new growth pro- 

 duced after plants are cured is normal. In this respect these viruses are like 

 the growth-promoting substances. Their effects do not outlast the periods 

 during which they are allowed to act but, unlike growth-promoting substances, 

 viruses cause a retardation of growth in all plants in which they are permitted 

 to multiply, although, as we have seen, they stimulate growth in certain tissues. 

 They also are entirely unlike growth-promoting substances in that they infect, 

 multiply, and cause disease. 



, Department of Animal and Plant Pathology 

 The Rockefeller Institute fof Medical Research 

 Princeton, New Jersey 



Literature Cited 



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 30: 866-869. 1940. 



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3. Jones, L. K., Anderson, E. J. .& Burnett, G. The latent virus of potatoes. Phytopath. 

 Zeitschr. 7: 93-115. 1934. 



4. KuNKEL, L. O. Histological and cytological studies of the Fiji disease of sugar cane. 

 Hawaiian Sugar Planters' Assoc, Exp. Bull., Bot. Ser., 3: 99-107. 1924. 



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 243-244. 1927. 



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7. KuNKEL, L. O. Heat cure of aster yellows in periwinkles. Am. Jour. Bot. 28: 761-769. 

 1941. 



8. KuNKEL, L. O. False blossom in periwinkles and its cure by heat. Science 95: 252. 1942. 



9. McWhorter, F. p. a latent virus of lily. Science 86: 179. 1937. 



10. Nishimura, M. a carrier of the mosaic disease. Bull. Torrey Club 45: 219-233. 1918. 



11. Samuel, G., Bald, J. G. & Eardley, C. M. "Big bud," a virus disease of the tomato. 

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