MICR O C HEM IS TR Y. 1 09 



woods, which usually contain in the cavities of the cells of 

 the medullary rays and of the wood-parenchyma, granules 

 of the same character as the pigments which incrust their 

 walls. 



Naegeli and Schwendener have studied from this point of 

 view the madder pigments and berberin, which have, how- 

 ever, recently been placed in other parts of the system of 

 organic compounds (cf. 158 and 212). 



187. According to the investigations of A. Rosoll (I, 137), 

 the yellow pigment contained in the bracts of the involucre 

 of various species of Helichrysum, which he calls helichrysin, 

 belongs to this group. According to Rosoll, it is associated 

 with the protoplasm in the young bracts, and only pene- 

 trates the membrane in old cells. Helichrysin has not yet 

 been studied macrochemically, but it is characterized micro- 

 chemically by being soluble with difficulty in cold 'water, 

 but readily so in hot water, alcohol, ether, and organic 

 acids. It is insoluble in benzol, chloroform, and carbon 

 bisulphide. Mineral acids, as well as alkalies, color it a 

 beautiful purple-red. Lead acetate precipitates the pigment 

 from its solution with a red color. 



188. It seems also probable, from the researches of Naegeli 

 and Schwendener (I, 504), that ant/wcyanin can incrust the 

 cell-walls under some circumstances. At least, the pigment 

 extracted from the seed-coat of Abrus precatorius showed a 

 relation to acids and alkalies quite corresponding to that of 

 anthocyanin ; while, on the other hand, membranes com- 

 pletely washed out were deeply stained by the cell-sap 

 pressed from red petals of flowers. 



/. Coloring Matters which only occur deposited in the Cell- 

 wall. 



189. Coloring matters with the above characteristic are 

 widely distributed among the lower plants. Thus two pig- 

 ments are found among the Cyanophycea, according to Nae- 

 geli and Schwendener (I, 505), glceocapsin and scytonemin, 

 which are completely restricted in their occurrence to the 



