FAMILY II. PELOPLOCACEAE 271 



The bands may reach a length of 700 mi- the surface of bottom mud along with 



crons. Beggiatoa, Thiospira, Zoogloea and similar 



Source : Found in Germany in ponds where types of bacteria. 



C/tara sp. was growing; also found by Beger Habitat: Presumably widelj' distributed 



(1954) in decomposing plant materials on in fresh-water ponds. 



Genus II. Pelonema Lauterhorn, 1915. 

 (Verhandl. Naturhist.-med. Verein z. Heidelberg, N.F. 13, 1915, 408.) 



Pe.lo.ne'ma. Gr. adj. pellos or pelos dark-colored; Gr. noun neina filament; M.L. neut.n. 

 Pelonema dark-colored filament. 



Long, unbranching trichomes, occurring singly, which are either straight or spirally 

 twisted. The trichomes are enclosed in a very thin, delicate sheath. Non-motile, but may be- 

 come motile. Within the trichomes are C3'lindrical, colorless cells which contain one or 

 several to many false vacuoles which emit a reddish gleam of light. Found on the surfaces 

 of ponds and lakes w^hich contain decomposing algae and which are poorly aerated. 



The type species is Pelonema temie Lauterborn. 



Key to the species of genus Pelonema. 



I. Cells contain a single false vacuole. 



A. Cells 8 to 12 microns long; trichomes are straight and attain a length of up to 300 

 microns. 



1. Pelonema tenue. 



B. Cells 4 to 6 microns long; trichomes are straight and are 200 or more microns long. 



2. Pelonema hyalinum. 

 II. Cells contain several to many false vacuoles. 



A. Trichomes are straight, measuring up to 500 microns in length. 



3. Pelonema pseudovacuolatum. 



B. Trichomes are spirally twisted, reaching a length of 40 to 160 microns. 



4. Pelonema spirale. 



1. Pelonema tenue Lauterborn, 1915. hy. a. li'num. Gr. adj. ^T/ahwi/s of crystal, 

 (Verhandl. Naturhist.- med. Verein z. glass; M.L. adj. hyalinus hyaline. 

 Heidelberg, N.F. 13, 1915, 408.) Straight trichomes which measure 200 or 



te'nu.e. L. adj. tenuis slender. more microns in length. The cells, 2 by 4 to 



Straight trichomes, up to 300 microns 6 microns, contain a single false vacuole 



long, which may become motile when the which is quite large and slightly refractive; 



water in which they are growing is low in the vacuole is rectangular in shape and has 



oxygen content. Cells are 2 by 8 to 12 mi- rounded edges. 



crons. Each cell contains a single false Source: From water from Little Ploner 



vacuole which nearly fills the cell; the Lake, Schleswig-Holstein, Germany, 

 vacuole is irregular in shape and emits but Habitat: Found in the upper algae-con- 



a small reddish gleam of light. taining layers of deep fresh-water lakes. 



Source: From pools in the Rheinebene, 

 Germany, where Chara was growing. 3. Pelonema pseudovacuolatum Lau- 



Habitat: Presumably widely distributed terborn, 1915. (Verhandl. Naturhist.- med. 



in fresh-water ponds and lakes which con- Verein z. Heidelberg, N.F. 13, 1915, 408.) 

 tain decomposing algae. pseu.do. va.cu.o.Ia'tum. Gr. adj. pseudes 



false; L. adj. vacuus empty; M. L. noun 



2. Pelonema hyalinum Koppe, 1923. vacuola a vacuole; M.L. adj. pseudovacuola- 

 (Pelonema hyalina (sic) Koppe, Archiv. f. tns having false vacuoles. 

 Hydrobiologie, H, 1923, 625.) Straight trichomes measuring up to 500 



