7 6 THE POPULAR SCIENCE MONTHLY. 



dogwood, the yellow of the tulip tree, the brilliant purple of the 

 sweet-gum tree might doubtless be enhanced and modified and 

 made to appear at different seasons by intelligent selection and 

 change of conditions ; and travelers tell us that in the tropics, 

 where the struggle for existence is most severe, bright-leaved 

 plants are common. Why ? What are the uses of color ? Since 

 the publication of the works of Sprengel, Muller, Delpino, Hilde- 

 brand, and others, its attractive power has been so enthusiastically 

 studied that the thought of its having other meanings has been 

 largely lost sight of. 



Flowers are the hope of a plant ; their careful protection from 

 injury is of vital importance. They are, as a rule, so short-lived 

 that there must be special adaptation for the speedy fulfillment 

 of their function. On the other hand, the value of crossing is 

 so great that many of them have become partly dependent for its 

 accomplishment upon the aid of other organisms. But the very 

 provision made for the entertainment and attraction of these 

 friends also serves excellently the wants of numerous intruders 

 who would take the treasure without giving any equivalent for 

 its use. Therefore it is that among flowers (and fruits, to which 

 somewhat similar reasoning applies) we find the most marvelous 

 combinations of attractive and protective qualities, and, as with 

 animals, color is an important element in each. The very beauty 

 which is the Elysian field of some happy insect may be the 

 Gehenna of another. The essentials of a heaven are as varied as 

 individual tastes. Hence it is impossible to limit a given color to 

 one function. Use is many-sided, and while the attractive power 

 must still be emphasized, others should not be forgotten. Color, 

 like everything else, is always increasingly developed in propor- 

 tion to its usefulness, and accordingly most common and most 

 protean among flowers and fruits, although by no means confined 

 to them. 



I. Chemical Uses. — It has sometimes merely chemical uses. 

 The work of (green color) chlorophyl, the study of which is a 



science in itself, need not be dwelt on here. 



According to Pick, red color, too, has an important chemical 

 office, inasmuch as in its presence the food substances manufact- 

 ured by young, growing shoots (in which it frequently occurs) 

 are transported more rapidly, so making possible the desired quick 

 development of each organ, while those which are made last do 

 not remain in the autiiinn leaf to be lost with its fall, but are 

 speedily conducted to the winter storehouses. 



Photography shows that color changes the properties of light. 

 Stewart suggests that every flower by means of its color may 

 transform the sun's rays in accordance with its own needs. 



II. Protective Color. — The knight of the fairy tale who 



