1904.] KRAEMER — NATURE OF COLOR IN PLANTS. 259 



So-called White Colors. 



The so-called white colors in plants do not properly belong to 

 either class, but may be said to be appearances rather, due to the 

 absence of color, and depending upon the reflection of light from 

 transparent cells separated by relatively large intercellular spaces 

 containing air. In other words the effect produced by these cells 

 may be likened to that produced by the globules in an emulsion. 

 The white appearance is most pronounced in the pith cells of roots 

 and stems, where on the death of the cells the size of the inter- 

 cellular spaces is increased and the colorless bodies in the cells as 

 well as the walls reflect the light like snow crystals. 



Methods of Extraction. 



During this investigation I have examined by means of the Leitz 

 micro-spectroscope the various kinds of coloring substances to 

 which I shall refer but, except in the case of chlorophyl, did not 

 obtain results which were entirely satisfactory, and will endeavor to 

 give special attention to this phase of the subject in another paper. 

 It is frequently difficult to extract and isolate these substances in a 

 sufficiently pure condition for spectroscopic work, particularly as 

 many of them change rapidly. 



In this paper, therefore, I shall confine myself to the considera- 

 tion of the behavior of the extracted coloring substances toward 

 chemical reagents. 



The material containing the coloring matter was in all cases 

 separated as nearly as possible from that which was free from color 

 or contained it in less amount. Various solvents were used in the 

 extraction of the coloring substances, depending upon the solubility 

 or nature of the substance. The solvent mostly employed was 

 alcohol (95 per cent.), in some cases dilute alcohol (50 per cent.) 

 or water (hot or cold) was employed. 



The plastid colors were extracted by placing the fresh material 

 in 95 per cent, alcohol and allowing it to macerate in the dark for 

 a day or two. I usually took the precaution to tear the material 

 with the fingers rather than to cut it. The solution so obtained 

 contains other than the plastid coloring substances, which latter may 

 be isolated in a more or less pure condition by either of the following 

 methods : ( i ) The alcohol is distilled off" and the solution evaporated 

 on a water bath to near dryness, boiling water is then added and 



