D--Packets _Sarcina_ DD--No packets. E--Yellow pigment _Micrococcus_ EE--Red pigment _Rhodococcus_ BB--Rods: C--Spiral rods D--Short, comma-like rods. One to three flagella. _Vibrio_ DD--Long spirals. Five to twenty flagella. _Spirillum_ CC--Straight rods. D--No endospores. E--Rods of irregular shape or showing branched or filamentous involution forms. F--Cells irregular in shape. Staining unevenly. Animal parasites. G--Acid fast _Mycobacterium_ GG--Not acid fast. H--Cells elongated, fusiform _Fusiformis_ HH--Cells not elongated, sometimes branching. I--Gram positive. Slender, sometimes club-shaped. _Corynebacterium_ II--Gram negative. Rods sometimes form threads. Characteristic honey-like growth on potato. _Pfeifferella_ FF--Cells staining unevenly but with branched or filamentous forms at certain stages. Never acid fast. Not animal parasites. G--Metabolism simple, growth processes involving oxidation of alcohol or fixation of free N (latter in symbiosis with green plants). H--Cells minute. Symbiotic in roots of legumes. _Rhizobium_ HH--Oxidizing alcohol. Branching forms common. _Acetobacter_ GG--Not as G. Proteus-like colonies. H--Not attacking carbohydrates _Zopfius_ HH--Fermenting glucose and sucrose at least. _Proteus_ EE--Regularly formed rods. F--Metabolism simple, growth processes involving oxidation of C, H, or their simple compounds or the fixation of free N.--_NITROBACTERIACEÆ._ G--Fixing N or oxidizing its simple compounds. H--Fixing N, cells large, free in soil _Azotobacter_ HH--Oxidizing N compounds. I--Oxidizing NH₄ compounds _Nitrosomonas_ II--Oxidizing nitrites _Nitrobacter_ GG--Not as G. H--Oxidizing free H _Hydrogenomonas_ HH--Oxidizing simple C compounds, not free H. I--Oxidizing CO _Carboxydomonas_ II--Oxidizing CH₄ _Methanomonas_ FF--Not as F.