inclosed by a sheath; cell contents usually pale blue-green, rarely 

 brightly colored; cells 1.2-2.5/x in diameter, 10.5-1 8/^ long. 



Our specimens have not been collected from strata on rocks as 

 described for Anacystis Peniocystis ( Kuetz. ) Drouet & Daily ( Daily, 

 1942), but always as small planktonic colonies of more or less 

 definite shape. Our plants are assigned to this species on the basis 

 of cell size and shape, sheath characteristics and color. 



Rather common in the tychoplankton of lakes. Wis. 



Gloeothece linearis var. composita G. M. Smith 1920, p. 46 



PI. 103, Fig. 1 

 Differs from the typical form in having shorter, stouter cells, and 

 in the small number of individuals (2-8) within the broad colonial 

 sheath; cell sheaths not confluent; cells 3-3.5/* in diameter, 4-8/a 

 long; plants 10-12/t wide, 20-35/1, long. 



Appearing with the typical form in tychoplankton. Wis. 



Gloeothece rupestris ( Lyngb. ) Bornet in 



Wittrock & Nordstedt 1880, No. 2456 



[Anacystis rupestris ( Lyngb. ) Drouet & Daily in Daily 1942, p. 650] 



PI. 103, Figs. 2, 3 

 Cells ovate or cylindric-ovate, irregularly scattered throughout a 

 copious colorless or brownish gelatinous matrix, solitary or in 2's and 

 4's in small families surrounded by definite sheaths; plant mass 

 usually attached, at least when young, becoming free-floating; cells 

 4-6-(9)/x in diameter, up to 15/i, long. 

 Tychoplankter. Wis. 



RHABDODERMA Schmidle & Lauterborn in Schmidle 1900e, p. 148 



A free-floating, ovate or fusiform colony of 8-32 sigmoid or 

 arcuate cylindrical cells with rounded poles; individual sheaths 

 entirely confluent with the colonial mucilage which is thin, trans- 

 parent, without lamellations, and often scarcely discernible. 



Key to the Species 



1. Cells short, 5/j. or less in length, distinctly sigmoid R. irregulare 



1. Cells more than S/jl long, straight, weakly sigmoid or contorted 2 



2. Cells strongly twisted and contorted R. sigmoidea 



2. Cells straight or sHghtly sigmoid 3 



3. Cells straight or somewhat curved, 8-10/u. long R. lineare 



3. Cells curved or sigmoid, 10-14/* long R. Gorskii 



[462] 



