TAUBENHAUS: SILVER SCURF OF THE WHITE POTATO 55 1 



50 per cent.) mercuric bichloride, then rinsed five times in sterile 

 water to wash off all traces of the disinfectant. Tubes with agar 

 medium were liquefied and cooled down to the proper temperature. 

 With a flamed and cooled scalpel, a piece of the potato material 

 was placed at the mouth of the tube and thoroughly crushed, 

 and then shaken up with the medium. The content of the tube 

 was poured into a petri dish and allowed to cool. The first series 

 of cultures consisted of some fifty plates ; the spots cultured in this 

 case all showed sclerotia of Phellomyces sclerotiophorus biit not the 

 fruitings of Spondylocladium atrovirens. In four to five days, all 

 the plates showed a sclerotium-producing fungus, together with a 

 species of Fusarium. In some plates the latter predominated, 

 while in others the sclerotium-producing fungus predominated 

 (fig. 3). These two organisms were transferred pure, to slants 

 on agar medium. More isolations were made to the extent of 

 crushing 800 different spots of silver scurf and culturing in the 

 same number of plates. Of the spots selected in this case, 80 per 

 cent showed sclerotia in varying number, while the remainder 

 were free from it, free in so far as that none could be seen with a 

 hand lens. In all the plates, with but one exception, the sclero- 

 tium-producing fungus, together with the species of Fusarium, 

 appeared after four days. From these results, it appeared that the 

 sclerotium-producing fungus, that is, Phellomyces sclerotiophorus 

 was the predominating stage in silver scurf, and that the fruitings 

 of Spondylocladium atrovirens appeared very rarely or under certain 

 cultural conditions, yet to be determined. None of the plates 

 were discarded at once. In many instances, either the Fusarium 

 colonies or Phellomyces were so numerous that they overran the 

 plate, thus giving no chance for slower growing organisms to 

 appear. Fifty per cent of such plates were discarded and the 

 remainder kept for further observation. After about two weeks, 

 other minute fungus colonies appeared in about one per cent 

 of the plates (figs. 4 and 5). In the one petri dish where no 

 growth had previously appeared, there now showed the same 

 minute fungus colonies practically pure. These plates were 

 watched and transfers made on slants of agar. In five to six 

 days the fungus under observation produced the typical fruitings 

 of Spondylocladium atrovirens. Pure cultures (fig. 6) were now 

 easily obtained of this fungus, as well as of Phellomyces sclerotio- 



