THE SUSCEPTIBILITY OF THE PLANT CELL TO VIRUS DISEASE

A number of spraying experiments showed that the virus cannot enter a plant unless some of the cells are injured. It is not essential that such injury should be brought about in the presence of the virus. The chances of infection fall off rapidly in the first few minutes after injury, but infection occurs occasionally as long as half an hour after the cell is damaged.
Inoculations by micropipette into single cells of the host plant yielded only about one-tenth of the expected number of infections. This suggests differences in the susceptibility of the cells to virus attack.