PIGMENTS 285 



vital that they may be regarded as the most important sub- 

 stances in plants and animals. 



Pigments. It is chlorophyll, the pigment that enables plants 

 to make sugar which is the foundational substance for all others 

 in plants, that makes plant pigments important. Chlorophyll is 

 complex, the formula commonly given being C 5 5H 7 2O 6 N 4 Mg. 

 Associated with chlorophyll are carotin (C 40 H 56 ) and xanthophyll 

 (C 4 oH5 6 O 2 ), pigments that are usually yellow or orange. These 

 pigments are considered decomposition products of chlorophyll. 

 They produce most of the yellow and orange colors of fruits, leaves, 

 and flowers. Carotin is so named on account of being especially 

 prominent in the roots of Carrots. Anthocyan, whose formula 

 has not been satisfactorily determined, is a pigment occurring in 

 solution in the cell sap and produces the reds, purples, and blues, 

 being red or blue according to whether or not the cell sap is acid 

 or alkali. Aside from their use in plants in the manufacture of 

 food, pigments produce showy colors in flowers, fruits, and leaves, 

 thus adding charm to plants and assisting in pollination and in 

 the dissemination of fruits and seeds. The color of fruits has 

 much to do with their market value. Plants, like the Barberry, 

 owe much of their charm to their red berries, and plants, like the 

 Coleus, owe their charm to their highly colored leaves. 



Minor plant substances. Substances occurring in plants and 

 of less importance than those previously discussed, are the vola- 

 tile oils, glucosides, alkaloids, organic acids, and tannin. Just 

 what function they all have in plants is not known. 



Volatile oils. The volatile oils, unlike the fatty oils, evapo- 

 rate into the air, thus producing the plant odors. For making 

 perfumes they are extracted and commonly sold as essences. 

 Rose water, otto of Roses, Lemon oil, Clove oil, Bergamot oil. 

 Peppermint oil, Cinnamon oil, etc., are familiar examples of vola- 

 tile oils. Nearly all contain only carbon, hydrogen, and oxygen, 

 and some tines oxygen is absent. Commonly they are secreted 

 by special glands in the flowers or on the leaves and stems. 



Here may be mentioned the resins which are supposed to be 

 formed from certain constituents of the volatile oils. Some ex- 

 amples are the turpentines and rosin from pine trees, balsam from 

 Fir trees, and balsam of Peru. 



Glucosides. Glucosides, so named because they commonly 

 contain glucose as one of their constituents, are common in the 



