Kingdom Mychota [33 



organisms of this group, occurring in symbiotic combinations with larger bacteria or 

 with protozoa, have been named as additional genera; one of these is Chlorobacterium 

 Lauterborn, but the name is a later homonym. 



Order 2. Sphaerotilalea nom. nov. 



Order Desmobactcrialcs Pribram in Jour. Bact. 18: 376 (1929); there is no cor- 

 responding generic name. 



Cells colorless, elongate, in sheathed filaments which branch freely in the manner 

 called "false": the cells divide strictly in one plane; those at a distance from the tip 

 may so multiply as to break the continuity of the series by pushing a growing point 

 laterally out of the sheath. The cells may escape from the filaments, become lophotri- 

 chous, and function as swarm spores. There is a single family: 



Family Sphaerotilacea [Sphaerotilaceae] Pribram 1. c. There is probably only 

 one species, Sphaerotilus natans Kiitzing {Cladothrix dichotoma Cohn). It is found 

 as minute gelatinous colonies fioating on stagnant water; cells 2-4^ in diameter. 



Order 3. Coccogonea [Coccogoneae] (Thuret) Campbell Univ. Textb. Bot. 84 

 (1902). 

 Tribe Chroococcaceac [Coccogoneae) Thuret in Ann. Sci. Nat. Bot. ser. 6, 



1: 377 (1875). 

 Subclass Coccogoneae Engler in Engler and Prantl Nat. Pfianzenfam. I Teil, 



Abt. la: iii (1900). 

 Order Coccogonales Atkinson 1903. 



Orders Chroococcales and Entophysalidales Geitler in Pascher et al. Siisswasserfl. 

 Deutschland 12: 52, 120 (1925). 

 Cells solitary or colonial, not filamentous, never flagellate; mostly of blue-green 

 color and living by photosynthesis. 



Kirchner (in Engler and Prantl, 1898) placed here two families, Chroococcaceac 

 and Chamaesiphonaceae, but the second belongs to the following order. A proper 

 second family includes the colorless organisms of genus Achromatium. 



Family 1. Chroococcacea [Chroococcaceac] (Nageli) Rabenhorst Kryptog.-Fl. 

 Sachsen 1:69 (1863). Order Chroococcaceac Nageli Gatt. einzell. Alg. 44 (1849). 

 Unicellular or colonial blue-green algae. Chroococcus, Gloeocapsa, Merismopedia, 

 Coelosphaerium, Gomphosphaeria, etc., occur as plankton or as masses on damp 

 surfaces or the bottoms of bodies of water. Certain species occur as symbionts or 

 parasites within the cells of the green algae Glaucocystis and Gloeochaete. The re- 

 sulting bodies, having the color of blue-green algae with the structure of green 

 algae, resisted classification until Geitler (1923) explained their nature. 



Family 2. Achromatiacea [Achromatiaceae] Buchanan. Cells solitary, large, ellip- 

 soidal, without flagella, non-pigmented; protoplasm alveolar, with or without 

 granules of sulfur in the alveoli. Half a dozen species have been described; Bersa 

 (1920) was probably correct in reducing all to the original one, Achromatium 

 oxaliferum Schewiakoff. It occurs on mud under still waters rich in organic matter. 



Order 4. Gloiophycea [Gloiophyceae] Rabenhorst Kryptog.-Fl. Sachsen 1 : 56 



(1863). 

 Tribe Nostochineae {Hormonogoneae) Thuret in Ann. Sci. Nat. Bot. ser. 6, 

 1: 377 (1875). 



