184 LIVING PLANTS 



of the petiole of a leaf containing patches or 

 spots of color is placed in an aniline solution. 

 The dye will pass most quickly and rapidly to 

 the regions containing anthocyan, indicating 

 that the loss of water has been greatest from 

 these areas. 



The maintenance of a transpiration stream, 

 laden with mineral salts, to leaves and rapid- 

 ly growing shoots in an already moist and 

 w^arm atmosphere is a matter of some diffi- 

 cult3^ and importance. If the temperature of 

 a plant is higher than the surrounding atmo- 

 sphere it may continue to carry on transpira- 

 tion because of the greater tension of the 

 aqueous vapor in the heated air of the inter- 

 cellular spaces than in the surrounding med- 

 ium The presence of anthocA^an would be 

 almost a necessity to leaves under such cir- 

 cumstances. 



In connection with the heat producing prop- 

 erties of anthocyan it is to be said that it may 

 increase the amount of odorous substances 

 volatilized from fragrant flowers, and thus in- 

 directly aid pollination. It is also possible 

 that the actual warmth of organs containing 

 anthocyan may serve as a lure to animals. 



A number of pigments of limited distribu- 

 tion occur in the citrus fruits, colored algas 

 and bacteria, which are but little known so 



