COLORING MATTERS. IO/ 



and flocculent and passes into the cell -walls. 

 Potassic hydrate colors it purple, and causes its 

 escape into the surrounding medium. Chloride 

 of iron colors it orange and finally brownish-red. 

 Alcohol dissolves the fresh yellow pigment, but 

 not that which has been reddened by exposure to 

 the air. 



INDICANE, INDIGOTIN. 



Although the chemical investigation of this 

 substance in the living cell has so far been very 

 unsatisfactory, it will, no doubt, be of inter- 

 est to histologists for us to call attention to it 

 again. 



In the cells of the flowers of certain orchids, 

 especially Phajus, a blue substance is formed when 

 the plant dies. It occurs either as distinct crystals 

 or groups of crystals, and as small but numerous 

 granules. These may be readily produced by crush- 

 ing the parts of the flower, or by treating them 

 with alcohol. Micro-chemical analysis shows this 

 substance to be indigotin ; it is, therefore, proba- 

 ble that indicane previously existed in the cells, 

 possibly in small protoplasmic (?) granules (Tro- 

 phoplasts ?). The only micro-chemical reaction 

 for this substance at present known is its forma- 

 tion by alcohol. It can be sublimated, and after- 

 ward forms small crystals. 1 



1 Cf. Bommer : Bleuissement des fleurs de Phajus, etc. ; Just's bot. 

 Jahresbericht, 1874, II., 2, p. 868. 



