134 PLANT DISEASES 



or less wrinkled and puckered, and covered with a delicate 

 cobweblike white mycelium. All such are destroyed by 

 the parasite at a later stage of development. 



The parasites, so far as at present observed, belong to 

 Vertidllium and Mycogone, and are supposed to be con- 

 ditions in the life-history of some species of Hypomycts, 

 but this has not been demonstrated. 



PREVENTIVE MEANS. All diseased mushrooms should 

 be carefully removed and burned as soon as they appear, 

 otherwise the spores, which are formed in immense num- 

 bers, are diffused by wind, etc., over every part of the 

 cave or cellar, and settle down on the soil when a new 

 bed is prepared, and thus extend the disease. Spraying 

 the walls and soil, in fact every internal part of the building, 

 with 2\ per cent, of lysol before the spawn is deposited, 

 destroys all spores present, and has been found to materi- 

 ally reduce the disease ; it also destroys various insects, 

 more especially Sciara ingenua, which often proves very 

 destructive to the mushroom crop. The spores or germs 

 of many kinds of mushroom disease are undoubtedly 

 introduced along with the spawn. This danger can be 

 avoided by using artificially prepared spawn formed from 

 pure cultures of mycelium, which are placed in sterilised 

 material. A further advantage in this method is that any 

 particular strain of mushroom can be procured. This 

 method is now commonly adopted in France. 



A high temperature, and stuffy, stationary air, favour the 

 disease. 



Costantin and Dufour, Rev. Gen. Bot., vol. iv. pp. 401, 

 462, 549 ; vol. v. p. 497. 



