28 BACTERIA I FORMS AND REPRODUCTION 



are colourless, or rose, red, or violet never green. 

 The cells contain granules of sulphur. 



Family I. BEGGIATOACE^E. Colourless filamentous 

 forms. 



Genus I. Thiothrix. 

 2. Beggiatoa. 



Family II. Rhodobacteriacecz. Cells spherical, rod- 

 Shaped, or spiral, containing rose, red, or violet 

 pigment. 



