200 " Wilt " or " Crown-Rot " Disease of Carnations 



the laboratory and when inoculated into healthy plants produced 

 the disease. 



4. The 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. 



5. The fungus grows best at 25°-30° C, with something in 

 favour of the latter temperature. No growth at 0° C. or 40° C. At 

 15° C. growth less vigorous than at 25° C. : at 37° C. it remains feeble. 

 The fungus is not killed by incubation at 0° C. ; cultures from 0° C. 

 and 37° C. transferred to 30° C. showed a vigorous growth. No growth 

 occurred in cultures transferred from 40° C. to 30° C. 



6. The organism appears to be strictly aerobic. 



7. It withstands high degrees of acidity but less alkalinity. 



8. Conidia vary in size in different media and range between 

 14-85-37-95/x x 3-3-6-6/x, hyaline, fusiform to nearly straight, on some 

 media (banana) very small; 2-6 celled. 



9. Experiments 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. 



10. Field 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. 



11. It 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 cuttings in in 

 healthy ground; (d) pulling up and destroying all plants showing 

 any evidence of disease. 



12. Diseased 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. 



13. The 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 be the ultimate solution. 



The Botanical Laboratories of tin: 

 Union of South Africa, Pretoria. 

 January, 1915. 



