170 LIVING PLANTS 



Chlorophyll 



been impossible to determine their exact chem- 

 ical composition. 



Chlorophyll is perhaps the most important 

 coloring substance in the world, for upon this 

 substance depends the characteristic activity 

 of plants, the synthesis of complexcompounds 

 from carbon dioxide and water — a process 

 upon which the existence of all living things 

 is ultimately conditioned. Only in a very few 

 unimportant forms devoid of chlorophyll can 

 the synthesis of complex from simple com- 

 pounds, or from the elements, be accomplished. 

 The function of chlorophyll may only be com- 

 prehended when its chief physical properties 

 are understood. These may be best illustrated 

 if a solution of the substance is obtained by 

 placing a gram of chopped leaves of grass 

 or geranium in a few cubic centimeters of 

 strong alcohol for an hour. Such a solution 

 v^ill be of a bright, clear green color, and 

 when the vessel containing it is held in such a 

 manner that the sunlight is reflected from the 

 surface of the liquid it will appear blood-red, 

 due to its pro]3erty of Biiorescence, that of 

 changing the wave length of the rays of light 

 of the violet end of the spectrum in such 

 manner as to make them coincide with those 

 of the red end. It is by examination of light 

 which has passed through a solution of chloro- 

 phyll, however, that the greatest insight into 



