Family chlorobacteriaceae 



871 



the common green plant chlorophylls and from bacteriochlorophyll. Capable ol" 

 photosynthesis in the presence of hydrogen sulfide, but do not store sulfur globules 

 inside the cells. 



The type species is Pelodictyon clathr at i forme (Szafer) Lauterborn. 



Key to the species of genus Pelodictyon. 



I. Cells united in colonies in a net-like fashion. 



1. Pelodictyon. clathralifonnc. 



II. Cells arranged in tightly packed colonies without net-like structure. 



a. Colonies composed of irregularly arranged cell-masses, e.xtending in three 

 dimensions. 



2. Pelodictyon aggregatum. 



aa. Colonies consisting of parallel strands and extending in two dimensions. 



3. Pelodictyon parallelion. 



1. Pelodictyon clathratiforme (Szafer) 

 Lauterborn. {Aphanothece clathrati- 

 forme Szafer, Bull. Acad. Sci., Cracovic, 

 S6r. B,3, 1910, 162; Lauterborn, Allgem. 

 botan. Ztschr., 19, 1913, 98; Lauterborn, 

 Verhandl. naturhist.-medizin. Vereins, 

 Heidelberg, N.F. 13, 1915, 430; Pelodic- 

 tyon clathratiforme Geitler, Die Siiss- 

 wasserflora Deutschlands, Osterreichs 

 und der Schweiz, Jena, 12, 1925, 458; 

 Pelodictyon lauterbornn Geitler, ibid., 

 458.) From Greek clathros, trellis and 

 formis, shape. 



Cells: Generally rod-shaped, ranging 

 from slightly elongated ovoids to dis- 

 tinct rods, often vacuolated, about 0.5 

 to 1.5 micron by 2 to 4 microns, produc- 

 ing rather wide slime capsules, and 

 characteristically united into three- 

 dimensional colonies which present a 

 net-like appearance, with mazes of 

 about 10 to 50 microns. 



Color yellowish-green. Xon-motile. 



Abnormal cell forms (involution 

 forms) not uncommon, consisting of 

 elongated and curved, forked, or club- 

 shaped and swollen rods, occasionally 

 suggesting rudimentary branching at the 

 extremities. Such cells may be found 

 as elements in chains for the greater 

 part composed of normal individuals. 



Habitat: Mud and stagnant water con- 

 taining rather high concentrations of 

 hydrogen sulfide and exposed to light; 

 sulfur springs. 



Illustrations: Szafer, loc. cit., PI. VI, 



fig. 5; Perfiliev, Jour. Microbiol. (Rus- 

 sian), 1. 1914. PI. II, fig. 1, 5-12; Lauter- 

 born, loc. cit.. 1915, PI. Ill, fig. 33. 



2. Pelodictyon aggregatum Perfiliev. 

 {Aphanothece lutecla Schmidle, Beihefte 

 Botan. Cent., 10, 1901, 179; Schmidlea 

 luteola Lauterborn, Allgem. l)otan. 

 Ztschr., 19, 1913, 97; Lauterborn, Ver- 

 handl. naturhistor.-medizin. Vereins, 

 Heidelberg, X.F., IS, 1915, 429; Pelo- 

 gloea hacillifera Lauterborn, ibid., 430; 

 Perfiliev, Jour. Microbiol. (Russian), i, 

 1914, 197.) From Latin aggregatus, 

 leading together, grouping. 



Cells: Usually rod-shaped, about 1 to 

 1.5 microns by 2 to 4 microns, often 

 vacuolated, producing mucus capsules, 

 and united into irregularly shaped, 

 three-dimensional colonies in which the 

 cells are more or less tightly packed, 

 without orderly arrangement. Colonies 

 may attain a size of up to 1 mm; fre- 

 quently they are not fully compact, but 

 contain less dense areas, or appear per- 

 forated, thus forming transition stages 

 to Pelodictyon clathratiforme. 



Color yellowish-green. Non-motile. 



Abnormal cell forms (involution 

 forms) usually in the shape of elongated 

 and curved, forked or club-shaped and 

 swollen rods, occasionally suggesting 

 branching at extremities. 



Habitat : Alud and stagnant water, con- 

 taining rather high concentrations o£ 



