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THE JOURNAL 



OF THE 



BOARD OF AGRICULTURE. 



Vol. XIII. No. 5' 



AUGUST, 1906. 



THE SPREAD OF FUNGUS DISEASES BY MEANS 

 OF HYBERNATING MYCELIUM. 



Until recently it was assumed that fungi could only be 

 reproduced by means of spores, the equivalent of seeds in 

 the higher plants. As exceptions to this general statement it 

 has long been known that in certain instances, concentrated 

 masses of mycelium termed sclerotia, could give origin to a new 

 fungus independent of spores, but such instances were not com- 

 mon. It was also known that the mycelium of some kinds of 

 fungi travel for a considerable distance in the soil from the point 

 of origin, and under favourable conditions produce new plants 

 far away from the parent stock. 



Apart from such exceptions, all endeavours to arrest the 

 extension of parasitic fungi injurious to cultivated plants, has 

 turned on some method of destroying the spores. This line of 

 treatment assumed that the plant to be protected was free from 

 disease, until infected from without by means of spores. 



Recent research has shown this assumption to be too general, 

 and has proved on the contrary that in the case of many of the 

 most destructive fungi, spores play a very subordinate part, and 

 in some instances no part whatever, in continuing a disease from 

 one year to another. In such cases the perpetuation of the 

 fungus is insured by the presence of mycelium in the seed, tuber, 

 bulb, or whatever part of the plant is used for reproduction. 

 More than this, it is known that when once some plants are 

 infested, the mycelium present in the seed or tuber, as the case 

 may be, not only spreads along with the growing plant, but also 

 enters the new seeds or tubers and consequently the offspring of 

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