SUMMARY1The disease in the carnation here commonly referred to as “Wilt” or “Crown‐rot” is caused by a fungus belonging to the genusFusarium.2The disease usually shows as a wet rot of the stem just below the soil. The lower leaves turn a sickly colour, are usually more erect and soon the whole plant is dead.3This fungus was isolated from diseased carnations; grown in the laboratory and when inoculated into healthy plants produced the disease.4The organism grew well on all culture media, producing usually a greyish growth. Along the glass of the tubes and the bottom of Petri dishes, it showed shades of grey, yellow, brown and red.5The fungus grows best at 25o‐30oC, with something in favour of the latter temperature. No growth at 0oC. or 40oC. At 15oC. growth less vigorous than at 25oC.: at 37oC. it remains feeble. The fungus is not killed by incubation at 0oC.; cultures from 0oC. and 37oC. transferred to 30oC. showed a vigorous growth. No growth occurred in cultures transferred from 40oC. to 30oC.6The organism appears to be strictly aerobic.7It withstands high degrees of acidity but less alkalinity.8Conidia vary in size in different media and range between 14.85‐37.95μ× 3.3‐6.6μ, hyaline, fusiform to nearly straight, on some media (banana) very small; 2–6 celled.9Experiments were carried out in the laboratory with various disinfectants and fungicides; these experiments serve to act as a guide for experiments on the treatment of infected soil.10Field experiments carried out with the object of finding whether the application of quicklime or formalin solution to diseased soils would have any beneficial effect, tend to show:(a)the plot treated with formalin was no better than the control plots;(b)on the whole, the plots treated with quicklime fared a little better than the controls, but further experiments would be necessary.11It is urged that the spread of the disease should be prevented as far as practicable by:(a)growing one's own cuttings;(b)obtaining cuttings from healthy vigorous plants only; (c) laying Guttings in in healthy ground;(d)pulling up and destroying all plants showing any evidence of disease,12Diseased soil should be submitted to a judicious process of crop‐rotation for a few years, and all attempts made to prevent the fungus spreading from diseased to healthy areas.13The question of the existence of varieties more or less immune from the disease has thus far not received attention, though it is a problem well worth serious consideration, and the breeding of disease‐resistant varieties may yet