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ROTTENNESS OF TURNIPS AND SWEDES. [Sept. 1896. 



In a consideration of the cause of rottenness of the swedes 

 in the pits and the presence of a Botrytis upon those which are 

 decaying, the first problem to solve is whether this fungus is 

 directly responsible for the decay, and therefore a parasite, or 

 whether it is merely a saprophyte living upon the roots which 

 had already been killed. To answer these questions it was 

 necessary to undertake a series of special cultures to prove 

 whether the fungus had the power of penetrating and subsisting 

 upon the living tissue. The method employed was to cultivate 

 the fungus both upon sterile pieces of swede, turnip, potato, and 

 also upon turnips growing in the garden. 



In the first series of experiments test-tubes and small glass 

 bottles with the mouth plugged with cotton wool were employed,, 

 having been previously sterilized by exposure to a dry heat of 

 at least 120° C. for one hour, and often to a higher temperature 

 for a longer period. Pure sowings of eonidia could be readily 

 obtained from the sw T edes in the pits ; a decaying piece cut off 

 with a sterilized knife and inserted into a sterile tube produced 

 a crop of conidiophores and eonidia in a few days, which were 

 found to be free from any foreign eonidia. Pieces of perfectly 

 sound swedes were then first cut into blocks by means of a 

 knife sterilized before each cut by heating in the flame of a 

 bunsen burner, and these blocks were again recut with the same 

 precautions into the required shape for insertion into the bottles 

 or tubes. The eonidia were sown by means of a sterilized 

 needle upon the prepared pieces of swede, which were then 

 quickly introduced into the tubes, the cotton wool plug being 

 withdrawn with sterilized forceps and immediately replaced. 

 In the course of two or three days the spot where the eonidia 

 were sown was indicated by a brown patch, and a fine mycelium 

 could be seen at this place ; the brown discolouration gradually 

 proceeded throughout the entire block, while at the same time 

 the mycelium was actively developing, with the result that in 

 abo.ut a week the whole piece became brown and rotten, and 

 covered with a thick felt of aerial hyphse. 



The germination of the eonidia takes place very readily, and 

 can be easily observed in a hanging drop. The germ-tube is 

 protruded and soon grows out into a short hypha ; if the coniclia 

 are sown in water the development of the hypha is very limited, 

 but if sown in a nutrient solution the hypha soon branches, 



for the publication of his researches on a Botrytis which caused an epidemic upon 

 lilies in the damp summer of 1888; he furnishes a complete account of the biology 

 and life-history of the Botrytis and its action in secreting a ferment which causes the 

 dissolution of the cell-walls. 



Frank (Krankheiten der Pflanzen, 1896) has described a disease of the rape (cole- 

 seed) prevalent in the neighbourhood of Leipzig, caused by a fungus which produces 

 both Botrytis -eonidia, and also sclerotia upon the stems of the infected plants. The 

 sclerotia on germination gave rise to a Peziza. He was able to infect healthy plants 

 with the eonidia and also quotes the experiment of Hamburg, who infected the plants 

 from ascospores. Frank considers the Botrytis to be B. cinerea and a stage in the- 

 cycle of Sclerotinia {Peziza) sclerotiorum. 



