MYXOPHYCEAE 331 



Family 4 . Nostocaceae. H e t e r ocy sts intercalary 

 prominent. N ostoc, Cylindrosper 

 mum. 



Family 5. Scytonemataceae. Heterocysts intercal- 

 ary, not prominent. Scytonema. 



Family 6. Rivulariaceae. Heterocysts basal. Rivu- 

 laria. 



Family 7. Camptotrichaceae. No heterocysts. 

 Camptothrix. 



Family 8. Stigonemataceae. Heterocysts intercal- 

 ary, not prominent; cells in more than 

 one row. Stigonema. 



Order BACTERI-ALES. The Bacteria. Not green; typically 

 filamentous, but becoming few- or 

 one-celled by the solution of the fila- 

 ment. Related to the foregoing blue- 

 green plants. 



Sub-order THIOBACTERIA. With sulphur granules in the 

 cells. 



Family 9. Beggiatoaceae. Cells in motile filaments, 

 colorless. Beggiatoa. 



Family 10. Rhodobacteriaceae. Cells single, or in 

 colonies; red, rose or violet colored. 

 Chromatium. 



Sub-order EUBACTERIA. Without sulphur granules in the 

 cells. 



Family 11. Phycobacteriaceae. Cells in straight, 

 motionless filaments. Crenothrix, 

 Sphaerotilus. 



Family 12. Spirillaceae. Cells in spirally coiled, mo- 

 tile filaments. Spirillum, Microspira, 

 Spirochaete. 



Family 13. Bacteriaceae. Cells mostly single, elon- 

 gated, straight. Bacterium (no flag- 

 ella), Bacillus (surface flagella), 

 Pseud omonas (polar flagella). 



Family 14. Myxobacteriaceae. Cells elongated, with- 

 out flagella, growing in definite, slimy 

 colonies. C hondromy ces. 



Family 15. Coccaceae. Cells mostly single, spherical. 

 Micrococcus, Streptococcus, Sar- 



