COLOURS OF FUNGI 167 



instance occurring in Ascobolus, a genus of Discomycetes, 

 growing mostly on dung. The spores, at first colourless, 

 change through pale lilac to clear deep amethyst. In 

 Sporormia, a genus belonging to the Sphaeriaceae, and also 

 growing on dung, the spores are first colourless, then clear 

 green, afterwards purple, and finally opaque brown. 



In the great majority of instances the colouring matter 

 of spores is confined to the wall, and in some instances to 

 the outer layer of this structure, as in the examples men- 

 tioned above. In some cases the contents of the spore 

 are alone coloured, the wall remaining colourless, as in 

 many aecidiospores, the spores of Bactridium, etc. 



In hyphae that are coloured the colour is also generally 

 confined to the cell-wall, although Biffen states that in 

 some hyphae the colour is located in the contents, the 

 wall remaining hyaline. 



The flesh of many species of Boletus changes from white 

 or yellow to a deep indigo-blue when broken and exposed 

 to the air. Schonbein first showed that the flesh of Boletus 

 luridus possessed the property of turning an alcoholic 

 solution of guiacum blue. This was explained on the 

 assumption that the fungus possessed the property of con- 

 verting the oxygen of the air into ozone, and that the ozone 

 reacted on the guiacum, producing a blue coloration. 



Bourquelot and Bertrand have recently investigated this 

 point, and have observed that a similar property is pos- 

 sessed by numerous fungi belonging to various groups. 

 They have verified Schonbein's observation given above, 

 and consider the action due to the presence of an oxidis- 

 ing ferment present in the fungus. This ferment they 

 call tyrosinase. It is further, stated that those fungi whose 

 broken flesh becomes coloured in contact with air contain 



