Virus Disease: This disease can be detected by yellow mottled foliage on the plant. Experimentation has disclosed that this mottling is due to a genetic character which follows a uniform pattern in all leaves, or virus which is not as regular and varies from plant to plant or on the same plant. The yellow variegation is mostly of the virus type. Virus is a disease which can be transferred by grafting although not by handling plants, while in cases of the genetic character it can be transferred. In grafting, virus may cause the scion of a solid coloured variety to variegate, but many such variegations are due to a true genetic character. Such virus does not seem to affect the vigour of the plant. There is at present no known cure for the disease.