THE EVOLUTION OF PLANTS 49 



elements of the earth entered three storehouses, air, water and land. 

 Energy was stored in and released by the sun, being transferred to 

 the earth by means of light as well as other rays which are invisible. 

 The "creative concept" instituted life and chlorophyll, and the 

 primordial home of life functions, protoplasm. From this beginning 

 all forms of life have developed, carried on and on by reproduction. 

 These life forms draw on the storehouses of air, water and land for 

 physical materials which, when no longer needed by the organism, 

 decompose and return to the three storehouses. For energy, these life 

 forms draw on light, transforming it into heat, sound, chemical, elec- 

 trical and mechanical (muscular) energy as needed. 



Life plus elements plus flowing energy expresses itself not only in 

 reproduction but in growth, movement, sensitivity, and metabolism. 

 Of these five characteristics, metabolism is most constant. Every 

 moment of the cell's active existence is marked by the chemical 

 changes which assure it food and the removal of wastes. 



Green and Non-Green Plants. Chlorophyll bearing plants have a 

 unique function which no true animal shares, the manufacture of 

 food. Plants which do not make food, but live on other life forms as 

 parasites, are like animals as far as food source is concerned. Some 

 fungi depend on dead organic matter as a food source ; these sapro- 

 phytes perform a very useful work in assisting the return of such 

 dead organic materials to the three storehouses of air, water and 

 land, where they again become easily available to new life. The 

 importance of this cycle in man's welfare cannot be overvalued. 



Certain bacterial plants, though lacking chlorophyll, appear to 

 utilize chemical energy from compounds of iron, sulphur, and nitro- 

 gen, and to make simple foods. 2 This phenomenon only adds to the 

 confusion as to what is plant, what is animal, and what is life. Of 

 this we are certain : there is an intimate connection between life, the 

 sun, and the earth. It is the details of that intimacy which concern 

 us most in living in today's world. 



II EVOLUTION FROM ONE CELL 



In trying to understand life today and in trying to achieve some- 

 thing we do not have, a satisfactory adjustment among the many 

 forms of life, it should be helpful to review briefly the development 

 of the plant world as science interprets it. 



Natural Selection. Once the geologist discovered that forces both 

 great and small are operating day by day, changing the face and body 

 of the earth, it did not take him long to surmise that these forces had 

 been at work for quite some time. After gaming fairly accurate data 

 on the speed of "uranium-lead" formation in rocks, he began count- 

 ing backward and came up with some startling figures as to the age of 

 rock formations exposed by river cutting, mountain uplift, or drilling. 



2 Sears, P. B., Life and Environment, Columbia University, Teachers College, 

 Bureau of Publications, New York, 1939, pp. 108-9. 



