VERTICAL FARMING 



PART IV 



Soil Bacteria 



The most constantly active part of the soil is its bacterial life. 

 These are tiny little plants that are very close to the border line 

 of being animals, and are known by a number of popular and 

 slang names. They are the smallest known living organisms. 

 Some are so small that 50,000 of them lying side by side would 

 not measure over an inch, and a single drop of blood or milk 

 would form a desirable tenement for thousands to live in and 

 multiply. They reproduce very rapidly, usually in from 15 to 

 45 minutes. If unchecked, a single bacterium could multiply 

 to 17,000,000 in 24 hours. This reproduction is seriously 

 checked by lack of room, insufficient food and unfavorable sur- 

 roundings, such as. lack of air or too much water for some 

 and the reverse for others. They are also checked in their 

 development by the presence of their own excreta. They form 

 spores for their reproduction and for preservation and distribu- 

 tion. In the spore stage they can live over long periods of con- 

 ditions unfavorable for their growth and reproduction, and 

 then begin their work again when conditions are favorable. 

 The total number of bacteria is inconceivable, for they are in 

 the air, water, soil, and everywhere. 



Some of them are harmful, and their development should be 

 checked, while others are so helpful to mankind that every effort 

 should be made to encourage their growth. The different 

 forms require widely different conditions for their best growth. 

 One class thrives in an abundant supply of air, and are called 

 " aerobic." Another form, " anaerobic," get their oxygen from 



