THE AMERICAN BOTANIST 113 



bark, and stem characters, thus enabling one to name most 

 of the species when not in flower. The book is especially 

 good in gardeners' forms which one encounters. so frequent- 

 ly in public parks and large private estates. The nomen- 

 clature is in keeping with that of Bailey's "Cyclopedia of 

 Horticulture," to facilitate reference to the latter work 

 where additional information may be found. The book 

 contains 200 pages and costs a dollar. It may be obtained 

 of the author at Urbana, Illinois. 



The varied colors of flowers appear upon examination 

 to be due to a relatively small number of pigments. The 

 dandelion and other flowers having their colors borne by 

 small bodies in the cells called chromoplasts are colored 

 by a substance called carotin, but those whose colors are 

 due to pigments in the cell sap are nearly all colored by 

 anthocyanin. The most familiar occurrence of anthocyanin 

 aside from its presence in pink, red and blue flowers may 

 be seen in the young leaves in early spring, in the touches 

 of red that are found, here and there, on the leaves and 

 stems of mature plants, in the colors that appear on al- 

 most any part of a plant when it is attacked by disease 

 or injured by insects, and in the color that is developed 

 on the underside of the leaves of nearly all water plants 

 and of other leaves that last through the winter. Antho- 

 cyanin appears to originate through the oxidization of a 

 pale yellow substance called a flavone which is not to be 

 confused with the other yellow pigment, carotin or xantho- 

 phyll. In some way, cold influences the production of 

 anthocyanin, and the formation of sugar in the cells appears 

 to have the same effect. Nearly all red, blue and pink 

 flowers are colored by anthocyanin, but study has shown 

 that the word anthocyanin stands for a group of closely 

 related pigments and not a single one. The anthocyanin 

 which gives the dahlia and geranium their color is pelar- 



