Photosynthesis 49 



yellow rays — in building up carbon compounds from 

 the carbonic dioxide absorbed from the air and the 

 water absorbed by the roots from the soil. The whole 

 economy of Animate Nature depends on this process, 

 for, in the long run, animals depend on the plant 

 world for their food. 



Chlorophyll is a complex of four pigments, and is 

 characteristic of almost all plants except the Fungi. 

 It absorbs light and, in some way not clearly under- 

 stood, it enables some of this radiant energy (a small 

 fraction of the whole that floods the leaf) to be uti- 

 lized in reducing carbon dioxide in solution, so that 

 oxygen is liberated and carbon is retained to help in 

 forming organic compounds. The first product is 

 in all probability formaldehyde, but this never accu- 

 mulates, being changed immediately into higher 

 molecular compounds — namely, sugars and starch. 

 Reactions are set up between the carbohydrate prod- 

 ucts and the nitrates which are brought to the leaf in 

 the sap-current or transpiration-current, and these 

 result in the higher steps of synthesis which culminate 

 in the production of proteins. These proteins always 

 form an essential part of the living matter in all 

 organisms. 



The fundamental importance of this photosynthe- 

 sis is well summed up in Dr. MacGregor Skene's mas- 

 terly work on The Biology of Flowering Plants (1924, 

 p. 79). "The organic matter of which the green 

 plant is formed, and from the oxidation of which it 

 derives energy, the organic matter which parasitic 

 plants obtain from green ones, and all the organic 



