The Life of the Fly 



of the reason. Both of them turn blue, with 

 an admixture of green. A third species, the 

 bkiish boletus {Boletus cyanescens, bull., 

 var. lacteus, leveille), possess remarkable 

 colour- sensitiveness. Bruise it ever so lightly, 

 no matter where, on the cap, the stem, the 

 tubes of the under-surf ace : forthwith, the 

 wounded part, originally a pure white, is 

 tinted a beautiful blue. Place this boletus in 

 an atmosphere of carbonic acid gas. We can 

 now knock It, crush it, reduce it to pulp; and 

 the blue no longer shows. But extract a frag- 

 ment from the crushed mass : immediately, at 

 the first contact with the air, the matter turns 

 a most glorious blue. It reminds us of a pro- 

 cess employed in dyeing. The indigo of com- 

 merce, steeped In water containing lime and 

 sulphate of Iron, or copperas. Is deprived of a 

 part of its oxygen ; it loses Its colour and be- 

 comes soluble In water, as it was in the original 

 indigo-plant, before the treatment which the 

 plant underwent. A colourless liquid results. 

 Expose a drop of this liquid to the air. 

 Straightway, oxidization works upon the pro- 

 duct: the indigo is reformed. Insoluble and 

 blue. 



This Is exactly what we see In the boletl that 

 turn blue so readily. Could they. In fact, con- 

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