220 STATE BOAKD OF AGRICULTURE 



eight bacilli. This is three hours and oat^-half from the beginnint^ of the 

 multiplication. At the end of the tenth hour, following out the same 

 ratio of increase, there will be one million one hundred seventy-six thou- 

 sand live hundred and seventy-six. Computations made concerning tlie 

 multiplication of one micro-organism for a week's time, provided every- 

 thing were favorable, give startling results. 



Classification according to fission: 



1. Bacilli: 



a. Threads — bacilli united end to end in a row. 



2. Micrococci: 



a. Diplococci — micrococci arranged in pairs. 



b. Tetrads— " " " fours. 



c. Sarcines — " " " cubes. 



d. Streptococci — ** " " chains. 



e. Stapylococci — " " " clusters. 

 Zooglea — the massing of bacteria. 



LIFE REQUIEEMENTS OF BACTERIA. 



Like other plants bacteria demand proper conditions before they will 

 develop; food suitable for their assimilation, moisture sufficient for com- 

 plete solution of the food, a reaction neither sironjtrly acid nor alkaline, 

 and a proper temperature to favor their growth. Wheat will not grow 

 unless these factors are observed. If the soil is void of richness, the grain 

 of wheat sprouts end withers away; if moisture is wanting, it may not 

 sprout at all; if the temperature is low, it scarcely grows; and if the 

 reaction of the soil is wrong the life is stunted, as in the alkali tracts of 

 the west. Wheat will grow in some soils while in others it is poisoned. 

 Some fields will produce forty or fifty bushels to the acre, and other fields 

 will merely return the seed. Again there are those plants which will grow 

 where the wheat will not, illustrating the fact that each species of plants 

 has its optimum soil. Just as with higher plants, so it is with bacteria. 

 Some will grow well on a soil where others will not; on certain soils there 

 are those which will not develop at all. Each species of bacteria has a 

 soil which is best adapted to that species. There are however certain ele- 

 ments which are absolutely necessary to their growth and which must 



enter into their food. 

 Food. Nitrogen is one of them. Remove all traces of nitrogen from 



Nitrogen. their food and they will not grow. Absolutely pure fat will 



not undergo dt composition, neither will an absolutely pure 

 sugar solution ferment In fat there is no nitrogen and sugar is free from 

 it. The sources of nitrogen are however numerous. When bacteria act 

 upon a bald rock protruding above the ground, they do not gain their 

 nitrogen supply from the rock but from traces of ammonia in the air and 

 from the free nitrogen of the air. These substances which they gain from 

 the air they convert into nitric and nitrous acids and utilize what nitrogen 

 they need for their own economy. In the soil, decomposing organic 

 matter, such as decaying plants, is present to furnish the required nitrogen. 

 Water has enough nitrogenous material suspended in it and in solution to 

 provide a rich nidus for the multiplication of bacteria. Disseminated 



