GENERAL CHARACTERS OF BACTERIA 13 
Classification.— Unfortunately different systems of classifica- 
tion are used by different bacteriologists. To learn them all 
would be of little use to the student of agricultural bacteriology; 
but the various classifications have certain points in common and 
it is important to learn them. Bacteriologists are quite generally 
agreed upon the following groups: 
SPHERICAL BACTERIA (cocci): 
Streptococcus divides in one plane, so as to form chains (Fig. 
9, d). 
Micrococcus divides in two planes 
and does not form chains (Fig. 9, ¢). 
Sarcina divides in three planes, . - 
forming cubical masses (Fig. 9, e). paw, eon 
d eee rs rs -) 
ee $2 
Also other names, such as Dziplococ- 
cus for the cocci that occur in twos, 2 _ Showing different 
and Staphylococcus for the patho- types ‘of cocci. in b, ‘and ¢, 
genic cocci, are often used. mococets dy Streptococes; 
ROD-SHAPED BACTERIA: 
Bacillus produces spores and has peritrichic flagella. 
Pseudomonas does not produce spores, and has its flagella all 
at one end (monotrichic or lophotrichic). 
Bacterium has no spores or flagella. Having no flagella it 1s 
immotile. 
Some spore-producing rods have no flagella, and some peri- 
trichic rods produce no spores. Bacteriologists disagree as to 
whether to call these forms Bacterium or Bacillus. In this 
book we shall follow the usage of Migula who placed the 
former in the genus Baciertwm, the latter in the genus Bacallus. 
SPIRAL BACTERIA: 
Spirillum forms one or more complete corkscrew turns. 
Vibrio forms only part of one turn. 
HicHER Bacteria (Cladothrix, Actinomyces, and others) (Fig. 10): 
Under this head are included several kinds of microédrganisms 
intermediate between bacteria and higher fungi. Unlike true 
