MICR CHEMIS TRY. I O I 



of macroscopic investigations and has hitherto produced 

 very few results of physiological value. 



After the discussion of these four pigments, the coloring; 

 matters of the chromatophores of the algae which are not 

 green will be taken up. 



a. Chlorophyll-green. 



169. The chloroplasts or chlorophyll-grains seem to owe 

 their color in all cases to one and the same coloring matter,, 

 to which is commonly given the name chlorophyll-green, or 

 chlorophyll. It is macrochemically distinguished by its. 

 strong red fluorescence and by its absorption spectrum, in 

 which may be distinguished four bands, besides the end 

 absorption beginning in the blue. Of these the strong band 

 in the red is especially characteristic. Since no other green 

 coloring matter has yet been observed in the chromatophores^ 

 it is only in case of feebly colored chloroplasts that any 

 doubt can arise as to the presence of chlorophyll in micro- 

 scopical observation. In such cases the so-called Jiypochlorin 

 or chlorophyllan reaction has been used for the recognition 

 of chlorophyll-green. According to A. Meyer (II), this 

 reaction is best conducted by treating the sections under a 

 cover-glass with glacial acetic acid. There are then ex- 

 truded on the surfaces of the chromatophores, sometimes 

 crystalline, sometimes amorphous masses which contain 

 decomposition-products of chlorophyll. For further reac- 

 tions of hypochlorin, see A. Meyer, II. 



ft. Carotin, Chlorophyll-yellow. 



170. Carotin was first prepared from the roots of Dancus 

 Carota, where it occurs in the form of rhombic plates or 

 variously shaped crystalline formations (cf. 356). The 

 same substance also occurs in the orange or red chromat- 

 ophores of many flowers and fruits. But, according to the 

 researches of Arnaud (II), it is constantly to be met with 

 within the chloroplasts, which, according to Immendorff (I), 

 contain no yellow or yellowish-red coloring matter except 

 carotin. Carotin would thus be identical with the coloring; 



