SUMMARY 125 



generation. A second leaf is soon started from the basal por- 

 tion; the first leaf unfolds in the light and the cells become filled 

 with chlorophyll ; the rhizome elongates by apical growth through 

 the ground until the young fern plant is fully established and is 

 ready to make and store up starch. The prothallium gradually 

 shrivels up and disappears. 



The work done by the fern is duplicated by every type of 

 plant life provided with chlorophyll. Sugars, starches, proteids 

 and lifeless woods are manufactured and stored in roots, fruits, 

 seeds and trunks, and with them is locked up the potential 

 energy to be transformed into kinetic energy by physiological 

 and physical combustion by man and the lower animals. Noth- 

 ing is wasted in the life cycle of matter and energy. Sugars, in 

 addition to their food value for animals and plants, in the 

 presence of yeast are transformed into alcohol and carbon dioxide 

 and their contained energy is changed into heat, energy of yeast 

 proteid and that of alcohol. Alcohol in the presence of bacteria 

 is turned into acetic acid, the potential energy being converted 

 into that of bacteria proteid and that of acetic acid. The latter 

 is acted upon again by bacteria and changed into carbon dioxide 

 and water in which the contained energy is nil, the bacteria 

 protoplasm again storing up that which was contained in the 

 acetic acid. 



The proteids, carbohydrates and fats, derived mainly from 

 plants, in the last analysis are the main food staple of all animals 

 and their chief source of energy. Both plants and animals re- 

 lease the stored energy in the form of heat and movement and 

 in metabolism give off nitrogenous waste, carbon dioxide, and 

 water. Of these, the nitrogen-holding substances only, still 

 holds some energy of combination. Under the action of 

 bacteria this small store is transformed into energy of bac- 

 terial proteid while free ammonia, carbon dioxide and water 

 are returned to the earth and the air (NH^CO + 2H 2 O 

 = 2NH 3 + CO 2 + H 2 O. The proteids of the dead bodies of 

 plants and animals after furnishing food and energy for scaven- 

 gers of many kinds are finally attacked by the army of nitrify- 

 ing and other bacteria and slowly transformed into nitrites, 



