A Three-fold Development. 153 



plements, few in number, rude in workmansMp and gen- 

 eral in use. As man has fougiit his way up from primi- 

 tive savagery to cultured civilization, he has continually 

 developed an increasing speciallization. So has it been 

 among the lower plants and animals. Let us study the 

 forms of plant life from the present as far back as we 

 can go and see if they will tell us anything concerning 

 the condition of the inorganic world when they lived. 

 The plant, as we know, derives a large part of its nutri- 

 ment from the carbonic acid of the air. Its leaves are 

 the organs through which this nutriment is absorbed and 

 assimilated for the building up of the growing organism. 

 Therefore, we should expect to find the leaf surface of 

 the plant proportioned to the amount of carbonic acid in 

 the air by which it was surrounded. An examination of 

 fossil plant remains will show us a continually decreas- 

 ing leaf surface until, as we go backward in time, leaves 

 will have entirely disappeared. The first plants were 

 without leaves, and the ends of the small branches were 

 mere buds or only rounded off. We know that the neces- 

 sary condition of existence is, and always has been, that 

 each organism should be in harmony with its surround- 

 ing conditions, and, therefore, we are compelled to be- 

 lieve that the supply of plant food must have been very 

 much greater at the beginning of plant life than it now 

 is, and that it has been gradually but surely taken from 

 the air from that time to the present. As matter is in- 

 destructible and can only be changed in form, we must 

 ask what has been the cause of this gradual decrease, 

 and where has the excess of carbonic acid gone to. The 

 plant stores up the carbonic acid in the form of carbon, 

 and so builds itself up. Now if a plant dies and decays 

 on the surface of the ground, or is burned, the carbon 

 in it again unites with a certain portion of oxygen, and 

 again becomes carbonic acid. But if the plant is pro- 

 tected from decaying, then it holds on to its carbon. 

 An examination of a piece of mineral coal under the 

 microscope shows us that it is almost entirely composed 

 of plant remains. The immense coal beds found in all 

 parts of the world, answer our question at once as to 

 where the excess of carbonic acid has gone to. There is 

 at present only about four parts of carbonic acid in each 



