VEGETABLE CYTOLOGY 



93 



Balsams are mixtures of resins with cinnamic or benzoic acid or 

 both and generally a volatile oil. Examples: Balsamum Tolu- 

 tanum, Styrax, Balsamum Peruvianum. 



If sections of a resin containing plant part are placed in a saturated 

 aqueous solution of copper acetate for a week or two and mounted 

 in dilute glycerin, the resin will be stained an emerald green. 



24. Pigments. These are substances which give color to various 

 plant parts in which they are found. They occur either in special 

 protoplasmic structures, as chloroplasts, chromoplasts or chroma- 

 tophores, or dissolved in tjae cell sap. Of the pigments named 

 the following will be considered: Chlorophyll, Xanthophyll, 

 Chromophyll, Etiolin, Anthocyanin, Phycocyanin, Phycophaein, 

 and Phyccerythrin. 



Chlorophyll is the yellowish-green pigment found in the chloro- 

 plastids or chromatophores of leaves or other green parts of plants. 

 Its composition is not definitely known although it yields products 

 similar to the haemoglobin of the blood when decomposed. Iron 

 is known to be essential to its formation. If an equal portion of 

 xylene be added to a fresh alcoholic solution of chlorophyll and the 

 mixture shaken, the chlorophyll in solution will break up into a 

 yellowish and greenish portion. The greenish portion dissolves in 

 the xylene which rises forming the upper stratum, while the yellowish 

 portion dissolves in the alcohol forming the lower stratum. To this 

 isolated greenish portion of chlorophyll has been given the name of 

 " chlorophyllin " while the yellowish portion has been designated 

 "xanthophyll." 



Chlorophyllin when examined spectroscopically produces absorp- 

 tion bands in the red, orange, yellow and green of the spectrum, the 

 broadest and most distinct band being in the red. 



Chromophyll also called " xanthophyll" and "carotin" is the yellow 

 or orange pigment found in chromoplastids. By some the term 

 carotin is limited to the orange pigment found in the carrot. Sul- 

 phuric acid forms a blue color with chromophyll. 



Etiolin is a pale yellow pigment which appears when green plants 

 are kept for some time in darkness. It is probably identical with 

 xanthophyll. 



