MYXOPHYCEAE 331 



Family 4. Nostocaceae. Heterocysts intercalary 

 prominent.^Nostoc, 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 Bactehiales. 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. — BeggiSitoa. 



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), 

 Pseudomonas (polar flagella). 



Family 14. Myxobacteriaceae. Cells elongated, with- 

 out flagella, growing in definite, slimy 

 colonies. — Chondromyces. 



Family 15. Coccaceae. Cells mostly single, spherical. 

 • — Micrococcus, Streptococcus, Sar- 

 cina. 



