ORGANIC REMAINS IN SOIL 427 



the earth. This energy has built up the plants through the carbon diox- 

 ide of the air and the water of the ground, and, according to H. Wagner, 

 the amount of living substance, very largely plants, if spread equally over 

 the surface of the earth, would cover it to a depth of one-fifth of an inch. 

 In general, the biosphere is much thicker and locally the depth of it rises 

 into feet. 



Mr. AV. L. McAfee estimated that an acre of woodland soil, about one 

 inch thick, near Washington, D. C, contained of easily seen organic re- 

 mains far more than 1,000,000 animals and over 2,000,000 fruits and 

 seeds. In meadow or grass land of the same latitude, the animal remains 

 rise to the incredible sum of about 13,000,000 and the seeds to nearly 

 34,000,000 per acre. In warmer climates these figures would rise and in 

 cooler ones decrease. In these estimates no account is taken of the plants 

 rooted in the ground, nor of the errant animals; so that our statements 

 of tlie numbers of the macroscopic life are far below the actual amount 

 in these areas. The invisible organic world is equally important, for 

 K. F. Kellerman tells us that a fertile soil has from 15,000,000 to 300,- 

 000,000 bacteria to the ounce of soil. Even though from 10,000 to 

 100,000 individuals may be placed side by side in the length of one inch, 

 tliey regenerate tlie soils and help to make possible the growth of plants 

 and animals. "In spite of their small size, they are concerned with every 

 phase of our daily life, and by their incredible numbers and ceaseless 

 activity overcome tlieir apparent insignificance.'' Many of the decompo- 

 sition bacteria double their number in a few hours of time when their 

 environment is favorable. Other kinds of bacteria occur in the sea- 

 watcn- and in tlie bottom muds and oozes. At the lx)ttom of the shallow 

 seas tliere may be as many as 285,000 individuals in one cubic centimeter 

 of mud. Besides the decomposition bacteria, there are many other im- 

 portant kinds, like the denitrifying bacteria that throw down carbonate 

 of lime, and the iron- and sulphur-making ])acteria tliat are also very 

 abundant in favorable places. 



The microscopic plants are but one element leading to rock disintegra- 

 tion and rock alteration. Equally important are the easily seeable plants 

 and animals, and their quantity is overwlielming. The number of known 

 kinds of living plants and animals is now nearly 800,000, and the sum 

 will eventually run into the millions, and of many species there are bil- 

 lions upon billions of individuals, and in general we can say that most of 

 the organisms pass through the life cycle in about one year. At the ])ot- 

 tom of the deeper oceans occurs the transparent, gelatinous, dead organic 

 slime known as bathybius (Huxley at first regarded it as a sort of organic 

 Ursclileim and a primitive nioncr), wliich resembles protojilasm and 



