Dec.9, i9i8 Seedling Diseases of Conifers 539 



a characteristic grape-juice purple, which diffused through the agar. 

 This was not constant even for the same strain. The moniliform char- 

 acter of the microspores of this species can be very easily demonstrated 

 by growing the fungus on a thin layer of nutrient agar in a petri dish and 

 examining the culture from above with the compound microscope after 

 four or five days' incubation at room temperature. 



The cultures used by the writers were isolated from seedlings of jack 

 and western yellow pine from nurseries on somewhat alkaline and very 

 sandy soils in southwestern Kansas. It is not believed to be a common 

 organism on pine seedlings in most localities. 



One or more strains of Fusarium moniliforme were tested in five inocu- 

 lation experiments on jack pine in autoclaved soil. In two of these 

 experiments, inoculation ^was only light or moderately heavy, and the 

 pots inoculated with F. moniliforme suffered distinctly less from damping 

 off than the controls, which were rather seriously affected as a result of 

 accidental contamination. A virulent strain of Coriicium vagum also 

 proved a failure in one of the experiments, and the most virulent strains 

 of Corticium and Pythium were only slightly active in the other. The 

 results in the three remaining experiments, together with the results 

 from all the other fungi which were used in the same experiments, are 

 given in Table II, with the exception that the results of inoculation 

 with strains of Corticium, which were atypical or intermediate in viru- 

 lence, in experiment 31 are omitted. The results of the two larger ex- 

 periments seem to establish beyond any serious doubt the ability of F. 

 moniliforme to cause damping-off of jack pine on autoclaved soil when 

 'sufficient inoculum is added. Absolute final proof must, of course, 

 await compliance with Koch's postulates and should be based on inocu- 

 lation with single spore cultures. The cultures used in these experiments 

 were all from planted plates. Nevertheless all of those whose results are 

 reported were apparently pure, and in view of the number of strains and 

 of controls in experiments 3 1 and 60, the parasitism of the fungus 

 under favorable conditions is considered practically established. In 

 addition to the pots formally designated as controls, the 35 pots inocu- 

 lated with Trichoderma sp. and with unidentified or mixed cultures in 

 experiment 31 serve perhaps as still better controls, as they received m 

 the inoculum the same nutrient medium as was applied to the pots 

 inoculated with F. moniliforme. 



