112 BO TANICAL MICRO TECHNIQ UE. 



g. Coloring Matters whicli are deposited upon the Ccll-walL 



192. In many lichens colored compounds occur which are 

 attached externally to the membranes. They are mostly 

 crystalline, more rarely amorphous. 



Amorphous excretions of pigment were found by Bachmann 

 (IV, 27) only in two lichens, and he has named them, from 

 the lichens in which they occur, Arthonia-violet and Urceo- 

 laria-red. ArtJionia-violet occurs in all parts of Arthonia 

 gregaria and is especially distinguished by being somewhat 

 soluble in cold, but readily so in hot, water. It is also solu- 

 ble in alcohol with a wine-red color. It is dissolved by a 

 solution of caustic potash with a violet color, but is insoluble 

 in lime and baryta waters. It dissolves in sulphuric acid 

 with an indigo-blue color, passing later into mallow-red ; 

 and in nitric acid with a red color. 



Urceolaria-red occurs in the thallus of Urceolaria ocellata. 

 It is characterized microchemically by not being changed by 

 alcohol, lime-water, or ammonium carbonate. It is dissolved 

 with a greenish-brown color by caustic potasJi solution and 

 baryta-water, as well as by concentrated nitric and sulphuric 

 acids. A solution of calcium chloride decolorizes it. 



193. The substances already described elsewhere, emodin, 

 chrysophanic acid, and calycin (cf. 140, 141, and 165), 

 belong to the crystalline excretions of the lichen-fungi, as 

 also a series of other so-called lichen acids, which have here- 

 tofore been studied almost exclusively macroscopically (cf.. 

 Schwarz II and Zopf II, 401). 



But I will discuss somewhat more in detail certain recently 

 described fungus-pigments. 



a. Thelephoric Acid. 



194. Zopf (V, 8 1) designates as thelephoric acid a pigment 

 extracted from various species of Thelephora, whose solu- 

 tions are of a beautiful red color, while the solid crystalline 

 pigment has a violet-blue or indigo-blue color. This partly 

 forms an incrustation of the membrane, partly a crystalline 

 deposit upon it. 



