99 



to change to a bright yellow when ex[)o.sed to the .smoke ot 

 tobacco ! 



A proper amount of .sunlight is nece.ssary to evoke color. 

 Insects deepen and intensify the natural hue by the stimu- 

 lating effects of their friction. 



Insects may change the color of an individual Hower bv 

 puncture. 



Newbigin ascribes color in tlowers to the result of dimin- 

 ished vegetative power ; another has given an opinion that 

 change of color is due to "the struggle for life." 



It is well known to botanists that flowers change color 

 by the mere process of drying, while in press. 



A white Monotropa turns coal black, also yellow Ba})tisia : 

 some purple asters fade to white, and the white pap})us of 

 others turns red. 



A rain drop or a spider, remaining for a few moments 

 on a petal of a purple morning-glory, will leave a red spot. 



The sap in Borraginaceie, as forget-me-not, etc., is said 

 to be tirst strongly acid, l)ut that with age the acid disap- 

 pears. These flowers change from pink to blue. 



According to Louis Prang, yellow^ can be ol)tained by a 

 mixture of red and green. 



There are some indications that insects by their stinui- 

 lating influences may really evoke in a limited degree a 

 new or modifled tint by drawing some new element to the 

 surface, as suggested in Liriodendron. 



Many flowers as a whole, or their honey guides, change 

 color at the time of fertilization. probal)ly by the plant 

 diverting its energy at that time to the setting of the seeds. 

 Different reliable gardeners have stated that cuttings from 

 a blue Hydrangea hortensis frequently })roduce at flrst pink 

 flowers. This may be accounted for by the new, rich soil 

 and better nourishing, for according to the same authority, 

 when the plant gets pot-bound and starved, its flo^vers are 

 apt to come blue ! 



