121 



" Polyporic acid," formula, Cg H. O.,. constituting 43'5 per cent of the dry fungus. 

 It is an ochre-yellow powder, insoluble in water, but soluble with intense violet 

 colour in alkalies. It crystallizes from hot alcohol in small plates, having a bronzy 

 lustre. The salts also crystallize. It belongs to the aromatic series, and is related 

 to benzoic acid. 



A section of Boleti, notably B. luridus, contain a yellow colouring matter 

 which turns blue on exposure to air. Phipson has asserted that this was a deriva- 

 tive of aniline. But neither analine nor its salts have this property. Seeing,' that 

 the Indigo plant and the Woad fisatis) contain a yellowish substance called 

 Indi(jogcn, which is converted into Indigo-blue on exposure to air, I suggested, 

 some years ago, that D. luridus contained this Indigogen. I extracted about 21bs. 

 of the fungus with alcohol, and obtained a brownish-yellow extract, becoming 

 rapidly blue in air. But Indigo is a very stable substance which may be reduced 

 by organic matter to colourless Indi<in-white, and then again oxidised to Indigo- 

 blue on exposure, and this transition may be effected any number of times. The 

 pigment of Boletus, on the other hand, rapidly passes from yellow to blue, and 

 from blue to brown; while in the blue state it can be again reduced to yellow; but 

 when it has once become brown it seems to be destroyed, as I could not by any 

 means restore the blue colour. Indigo gives, in the spectroscope, a very definite 

 absorption band : in the blue matter of Boletus I could not detect .any special band. 

 The finally-resulting brown mitter was amorphous, acid, soluble in water and 

 alcohol, and appeared very similar to the humus-like bodies extracted from peat, 

 &c. It did not contain nitrogen. I could not, however, obtain tiie blue matter in 

 a pure state on account of its rapid decomposition, but it certainly contains neither 

 Indigo nor aniline. It has been stated that B. cijanescena yields a brownish -yellow 

 pigment, turned deep blue by sodium hypochlorite, and unaffected by weak alkalies 

 or acids, and that similar reactions occur with B. luridus, Satanas, calopus, and 

 variegatus. I found, however, that B. luridus was simply bleached, and not blued, 

 by sodium hypochlorite. No cyanogen compound is present. 



Now as to the Alkaloids. An alkaloid means literally a compound resembling 

 an alkali. The alkalis are potash, soda, and ammonia ; they have the well-known 

 effects of blueing vegetal reds, of forming salts with acids, of an acrid taste, a soapy 

 feel, and characteristic odours. Certain compact groups of carbon and hydrogen 

 which can pass entire from compound to compound, are thence called compound 

 radicles. The alkali ammonia, then, being composed of one atom of nitrogen to 

 three atoms of hydrogen, can have its hydrogen replaced by one or more of these 

 compound radicles. So we form a '^compound avirnonia," or " amine." These 

 "amines" partake of the characters of the alkali ammonia, and hence are called 

 alkaloids. They are generally colourless, alkaline in reaction, and form crystal- 

 lizable salts by union with acids. 



As a rule, they are powerful in their action on the system, hence the plants 

 which contain notable quantities of them are either medicines, poisons, or perhaps 

 condiments like pepper, or semi-medicinal foods like tea or coffee. For this reason 

 their study is a most important feature of plant-chemistry. 



From ammonia (NH ^), by substituting the "compound radicle" methyl (CH ~ ) 



