DISTRIBUTION OF THE VIRUS OF THE MOSAIC DISEASE 

 IN CAPSULES, FILAMENTS, ANTHERS, AND PISTILS 

 OF AFFECTED TOBACCO PLANTS 



By H. A. Allard 



Assistant Physiologist, Tobacco and Plant-Ntitrition Investigations, 



Bureau of Plant Industry 



Embryonic transmission of the mosaic disease from parent to offspring 

 has not been observed in tobacco plants. Although the disease some- 

 times appears particularly malignant, so that normal capsule develop- 

 ment is almost completely inhibited and few viable seed are produced, 

 plants from such seed are healthy. The normal reproductive vigor of 

 tobacco plants may not be seriously checked by the mosaic disease, 

 especially if it makes its appearance late in the development of the 

 plant. In such plants a nearly normal vegetative development has been 

 attained and subsequent flowering and seed production appear to be 

 little, if at all, inhibited. 



It is of considerable interest to know how closely the embryo may be 

 invested with tissues bearing the infectious principle of the mosaic 

 disease. Before the question had been fully investigated the writer was 

 under the impression that the virus ordinarily did not reach the pla- 

 cental column bearing the seeds. In order to test this point, three 

 healthy Connecticut Broadleaf tobacco plants were set aside until seed 

 production had begun. The spongy placental tissue of six to eight 

 capsules on each plant was then punctured deeply with a needle and the 

 virus of mosaic disease introduced abundantly. Capsules of all ages, 

 from very young to those fully grown, were punctured and the virus 

 injected. Although a number of the more immature capsules developed 

 very poorly following this treatment, an abundance of seed was secured 

 and sowed on March 31, 1914. From this seed 400 plants were obtained 

 and later transplanted to 3-inch pots. On May 18 all were healthy, and 

 40 were inoculated with the virus of the mosaic disease. Practically all 

 of those inoculated were showing symptoms of the disease on May 27 

 and 28. 



Later experiments with affected plants have shown that the capsules 

 of such plants normally contain the virus of the disease. The tobacco 

 capsule contains two cells formed by a median cross wall or partition. 

 By cutting through the thin ovary wall near this partition on both sides 

 of the capsule the ovary wall can be readily removed in two halves, 

 exposing to view each half of the large placental column with its attached 



Journal of Agricultural Research, Vol. V, No. 6 



Dept. of Agriculture, Washington, D. C. Nov. 8, 1915 



ap G — 63 



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