100 BOTANICAL MICROTECHNIQUE. 



It is insoluble in fatty and ethereal oils, in benzine, carbon 

 bisulphide, chloroform, phenol, cold and hot water, and 

 dilute organic and inorganic acids. 



Since the membranes of the strongly thickened outermost 

 cell-layer of the seed-coat dissolve in concentrated sulphuric 

 acid with a deep-blue color, Harz concludes that spergulirt 

 is contained in the membranes themselves. 



8. Coloring Matters. 



167. The compounds united under this head do not form- 

 a group of chemically related substances, but there are in- 

 cluded here all colored substances whose chemical constitu- 

 tion is still too little known to enable them to be placed in 

 their proper position in the natural series. Concerning 

 most of them, then, our knowledge is extremely incomplete, 

 and an actual isolation and quantitative analysis has been 

 carried out with any exactness upon very few of them. 



It cannot be my duty to enumerate all the coloring mat- 

 ters heretofore extracted from various parts of plants. It 

 seems rather that I should restrict myself to those concern- 

 ing whose chemical relations we have some trustworthy 

 information, and which, especially, are microchemically 

 recognizable with some certainty. 



I have grouped the coloring matters according to the 

 place in the living plant where they occur. 



a. The Pigments of the ChromatopJiorcs. 



168. The different colorings of the chromatophores, ac- 

 cording to our present knowledge, if we omit for the 

 moment the algae which are not green, are to be referred to 

 a relatively small number of coloring matters. But these 

 are still too little studied to make a completely certain 

 limitation possible. Four coloring matters may be distin- 

 guished with some certainty, and I will here confine my- 

 self to their brief description. A special discussion of the 

 very abundant literature of chlorophyll does not seem de- 

 sirable here, since it contains almost exclusively the results 



