FUNGI 



187 



host organisms. The great work of fungi in nature is thus to 

 break down organic matter and return the elements to Mother 

 Earth, that they may be caught up in the circle of food supply 

 and live again. Without this beneficent work of the fungi 

 all the animals and plants 

 that have died since the 

 beginnings of life in the 

 world, if they had not been 

 eaten or burned, would still 

 cumber the earth ; that is, 

 the food of the world would 

 be locked up in dead forms. 

 Burning returns the nitro- 

 gen to the air, a most 

 wasteful process, -- while 

 the decay of the dead bod- 

 ies and waste matters of 

 animals and plants caused 

 by fungi holds this most 

 precious of all foodstuffs 

 in chemical combination as 

 nitrates, ready again to be 

 built up into the grains, 

 seeds, fruits, and other food 

 products of green plants 

 (see Chapter IX). Thus, 

 in burning wheat straw the 

 farmer may rob his land 

 of twenty-five pounds of 

 nitrogen in combination, worth $3.75 per acre per year, and 

 an acre of corn stover or cotton stalks may contain respec- 

 tively 17.50 and $15.30 worth of nitrogen. Where it is cus- 

 tomary to burn these materials is it any wonder that the wheat, 

 cotton, and corn fields are worn out? 



'NITRATES 



FIG. 90. Circulation of protein food 

 materials in nature 



Nitrogenous food (protein) is the one essen- 

 tial food of both animals and plants. The 

 green plants build up this entire food sup- 

 ply from the chemical elements by the 

 energy of sunlight working through leaf 

 green, or chlorophyll; nn represents free 

 nitrogen from the air, drawn into combi- 

 nation by symbiotic bacteria in the root 

 tubercles of clovers, beans, etc. The non- 

 nitrogenous foods starches, sugars, gums, 

 fats, and oils are built np along with the 

 proteins and are finally oxidized to carbon 

 dioxide and water, whether in the animal 

 or plant body or by rotting or burning 



