BACTERIA 



141 



plant debris and fragments of animals, insects, and worms, 

 in all stages of decomposition, ranging from their original 

 condition and easily recognizable, down to the unrecognizable 

 pieces and the amorphous, waxy coating on soil grains. The 

 whole mass of soil material, which at one time or another was 

 a part of living organisms, is called organic matter. Organic 

 matter in the process of decomposition, which is changing 

 continually and breaking down into new compounds, may 

 be called active organic matter. That particular part of it 





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Fig. 32. — Soil and subsoil, showing dark color due to organic matter. (Weir.) 



which is completely decomposed, which has lost all resem- 

 blance to living matter, and which is indistinguishable among 

 the soil grains, except that it gives the dark color to them, 

 may be called inactive organic matter or huftius. 



119. Bacteria. — As soon as a portion of a living organism 

 dies, whether it be a leaf, or bit of bark, or mass of roots, it 

 is at once attacked by bacteria which are everywhere present 

 in the soil. Inasmuch as bacteria are of such vital impor- 

 tance to agriculture, both beneficially and otherwise, a brief 

 description of them is desirable. 



