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Pomona College Journal of Economic lioxANv. 



in the soil, where diseased plants had prown, fffive evidence that the fungus 

 was also a soil funp:us and luifrht easily enter the plant throufih a wound. 

 To avoid infection from the soil all diseased plants should be destroyed 

 before the appearance of the conidia, a three-year rotation practiced, or the 

 soil disinfected. The latter method was suggested for small fanners who 

 would not be able to carry out a rotation of crops or for those who grew 

 carnations under glass. Experiments were conducted with carbon bisul- 

 phide, sulphate of iron, formaldehyde and naphthol, from which it was 

 found that all, with the exception of the la.st. would prevent the germina- 

 tion of the spores and the spread of the disease. Sulphate of iron cannot 

 be used in soils containing much calcium carbonate, for it decomposes too 

 quickly and does not kill the chlamydospores. Carbon bisulphide does not 

 act very well in clay soils. Formaldehyde may be used under varying 

 condition.s. 



FIELD OBSERVATIONS 

 In making the field observations thirteen nurseries were visited where 

 carnations are being grown on a commercial scale. These nurseries are situ- 

 ated in Elmhurst, Melro.se, Berkeley, and Richmond, and are owned by 

 Americans, Germans, Japanese, and Italians. The data obtained largely 

 corroborate that given by Jlr. L. Mangin in the foregoing pages. The 

 activity of the disease appears to be directly dependent upon cultural 

 conditions, and it is necessary to have a complete knowledge of the propaga- 

 tion of the carnation in order to understand the relation of the disease to 

 the plant. 



The carnation is commonly propagated by means of cuttings. The 

 cuttings are obtained by removing suckers or shoots, three or four inches 

 in length, from mature plants: the ba.se or heel of a cutting is cut off 

 squarely beneath a node, the lower leaves are entirely removed, and the 

 ends of the longer ones are usually clipped. In this locality cuttings 

 are started between the first of January and the first of ]\[arch; they are 

 rooted by being placed about one inch apart in boxes of sand, and kept in 

 the propagating house until a root system has developed, which is about 

 one month. The cuttings are then transplanted to other boxes or pots 

 containing ordinary soil, where they are set four to .six inches apart each 

 way. They are kept under glass until April or ^lay, then they are moved 

 outside, either in boxes or transplanted to the ground, where they remain 

 until moved into the houses used for the production of cut flowers. The 

 final tran.splanting is done in July or August, and the plants are placed 

 from ten to fourteen inches apart each way. During the colder months 

 the houses are heated by steam ; a temperature of 65 degrees to 70 degrees 

 F. is maintained during the day and 45 degrees F. to 55 degrees F. during 

 the night. On very warm days the temperature may rise above 70 degrees 

 F., but the grower makes every effort to keep it below 80 degrees F., by the 

 use of ventilators and overhead irrigation. Carnations will not thrive well 



