NOTABLE PHENOMENA. 115 



proceeds rapidly till ' the depth of intensity has been gained. 

 This blue colour is so universally confined to dangerous species 

 that it is given as a caution that all species which exhibit a blue 

 colour when cut or bruised, should on no account be eaten. The 

 degree of intensity varies considerably according to the con- 

 dition of the species. For example, Boletus carulescens is 

 sometimes only very slightly, if at all, tinged with blue when 

 cut, though, as the name implies, the peculiar phenomenon is 

 generally highly developed. It cannot be said that this change 

 of colour has as yet been fully investigated. One writer some 

 time since suggested, if he did not affirm, that the colour was 

 due to the presence of aniline, others have contented themselves 

 with the affirmation that it was a rapid oxidization and chemi- 

 cal change, consequent upon exposure of the surfaces to the air. 

 Archdeacon Robinson examined this phenomenon in different 

 gases, and arrived at the conclusion that the change depends on 

 an alteration of molecular arrangement.* 



One of the best of the edible species of Lactarius, known as 

 Lactarius deliciosus, changes, wherever cut or bruised, to a dull 

 livid green. This fungus is filled with an orange milky fluid, 

 which becomes green on exposure to the air, and it is conse- 

 quently the juice which oxidizes on exposure. Some varieties 

 more than others of the cultivated mushroom become brownish 

 on being cut, and a similar change we have observed, though 

 not recorded, in other species. 



The presence of a milky juice in certain fungi has been 

 alluded to. This is by no means confined to the genus Lac- 

 tarius, in which such juice is universal, sometimes white, some- 

 times yellow, and sometimes colourless. In Agarics, especially 

 in the subgenus Mycena, the gills and stem are replete with a 

 milky juice. Also in some species of Peziza, as for instance in 

 Peziza succosa, B., sometimes found growing on the ground in 

 gardens, and in Peziza saniosa, Schrad.,also a terrestrial species, 

 the same phenomenon occurs. To this might be added such 

 species as Stereum spadiceum, Fr., and Stereum sanguinolcntum, 



* Berkeley, " Introduction to Crypt. Bot." p. 266. 



