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-Nutrition 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, 
Dept, of Agriculture, Washington, D. C. 
Vol. V, No. 6 
Nov. 8, 1915 
