Abstract
Dew and rain water on mosaic tomato leaves contain free virus of the disease. Nicotiana sp. was used as test plant because the virus, which appears to be a strain of the ordinary tobacco mosaic virus, produces necrotic local lesions on the leaves. Samples of dew or rain water were gathered carefully from the surface of the mosaic tomato leaves and were filtered through “Seitz-Entkeimungs-Schichten”. The. filterates were then rubbed over the leaves of Nicotiana sp. which were dreviously dusted with finely ground carborundum abrasive. Within a few days after the inoculation, numerous local lesions peculiar to the virus infection appeared on the rubbed leaves.
Although the mechanism of the appearance of the virus in such water droplets is still obscure, it is highly probable, however, that the virus had not been brought to the surface of the leaves by such external agent as dust from the soil, because the virus was found to be in extremely low concentrations, in both the soil and the rain water of non-diseased plants.
