146 PLANT LIFE. 



the instant it is cut or broken and exposed to the air, it 

 assumes a deep indigo-blue colour. Schonbein's explana- 

 tion of this change is summarized as follows by De Bary — 

 " Schonbein has carefully examined this phenomenon, 

 and finds that it is a substance capable of being extracted 

 from the fungus by alcohol, and probably of a resinous char- 

 acter which turns blue in the air. The blue colour appears 

 in the alcoholic solution under the same conditions as it does 

 in a solution of guaiac-resin, and since it has been proved 

 that the colour is produced in the latter by combination 

 with ozonized oxygen, Schonbein assumes a similar cause 

 of the blue colour in the fungus. The alcoholic extract from 

 the Boletus does not by itself become blue when exposed 

 to the 'air; there must therefore be another substance con- 

 tained in the fungus, which ozonizes the oxygen of the 

 atmosphere, and then effects a combination with the resin, 

 giving off the oxygen to it in the state of ozone. Phenomena 

 of a similar kind, observed in other cases, confirm this 

 conjecture. Thus both the tincture of guaiac and the 

 alcoholic extract of Boletus turn blue at once, if they are 

 allowed to fall in drops on the fresh tissue of some of the 

 Agarici which do not themselves turn blue, especially 

 Agaricus sanguineus. The watery juice of Agarkus san- 

 guineus squeezed out from the plant and filtered, produces 

 the blue colour at once in both tinctures. From these facts 

 it may be concluded that a number of fleshy fungi contain 

 a substance soluble in water, which absorbs oxygen and 

 gives it up to other bodies in the state of ozone. The 

 Boleti which turn blue contain this substance, with another 

 resinous substance, which, like the guaiac-resin, is turned 

 blue by ozone." ^ 



' Fungi Mycetozoa and Bacteria, Engl, ed., p. 15. 



