THE AMERICAN BOTANIST 71 



yellow flowers are produced and which usually operates to 

 keep each genus or closely related group of plants to its own 

 color. Yellow flowers are colored by tiny grains called chro- 

 moplasts which are identical with the green grains or chloro- 

 plasts in every thing except color. Chloroplasts readily turn 

 to chromoplasts and thus all flowers have within them the pos- 

 sibility of becoming yellow. One recalls, in this connection, 

 how commonly the leaves turn yellow in autumn. It is the 

 facility with which a yellow color is produced that makes so 

 many of our flowers of this hue, and since yellow is so easily 

 made from green, it is quite natural that the simpler flowers 

 should oftenest have this color. That every yellow flower is a 

 simple flower, however, is by no means true. The highest 

 types of flowers in the world are the dandelions, hawkweeds, 

 and their allies, and these are nearly always yellow. Blue 

 flowers are due to a coloring matter in their sap which is not 

 so very far removed from the ordinary blueing. Most blues 

 are due to substances called anthocyanins, of which there are 

 many kinds. Under certain conditions (acid sap, for instance) 

 the blues may become pink or red, though most red flowers 

 are probably due to chromoplasts. Since the possibility of de- 

 veloping yellow is ever present, this color may appear even in 

 parts of otherwise blue flowers, as on a single petal, as a nectar 

 guide, etc. It may be added that the yellow lupine is an ex- 

 ceedingly showy plant and well worth growing in gardens. It 

 is offered for sale by some seedsmen, but appears to be diffi- 

 cult to germinate. — Ed.] 



