38 BACTERIA AND SOIL FERTILITY 



classification of bacteria are numerous. (l) The small simple 

 structure of the microorganism makes it impossible to work out 

 on a purely morphological basis a satisfactory classification as is 

 the case for the higher plants. (2) Many physiological charac- 

 teristics, such as pigment production, which at first sight may 

 appear useful, are not constant and hence cannot be used. (3) 

 Our knowledge of the characters of the bacteria even at the pres- 

 ent time is far from complete. (4) Bacteria play a part in 

 many fields of activity, and hence ihe criteria whereby they are 

 recognized vary greatly according to the art or science in which 

 they are studied. For agricultural and industrial purposes it may 

 be more practical and quite sufiScient to classify bacteria accord- 

 ing to their activity. For example, we may classify them as 

 butyric- or lactic- acid-producing, ammonifying, nitrifying, or 

 nitrogen-fixing organisms. (5) There has been a great tendency 

 for many authors to apply whole descriptions to microorganisms 

 instead of using the binomial names as agreed to in botany. For 

 instance, the following cumbersome unscientific designation has 

 been used: Micrococcus acldi faralactici liquefaciens Halensis 

 or Granulo bacillus saccharobutyricus immobilis liquefaciens. 



Migula's Classification of Bacteria-Numerous attempts 

 have been made to classify bacteria, but none are without flaws. 

 One of the most extensive used throughout America is the one 

 proposed about twenty-five years ago by Migula. Migula makes 

 use of morphology grouping of cell due to method of multiplica- 

 tion and motility. The classification as modified by Russell and 

 Hastings is given below: 



Suborder I. Haplobacteria. Bacterial cells not permanently united into fila- 

 ments without sheaths 



Family I. Coccaceae. Cells spherical, at least when free 



I. Cells non-motile 



A. Cell division in one plane, cells frequently remaining attached 



in chains Streptococcus 



5. Cell division in two planes (sometimes irregular), resulting in 



formation of flat plates or of masses of cells . . Micrococcus 

 C. Cell division in three planes, all at right angles, the cells remaining 



united after division, forming cubes or packets . . Sarcina 



