Radiofilum irregular e (Wille) Brunnthaler 1913, p. 7 



PL 7, Figs. 3-5 

 Filaments long, irregularly branched, branches often anastomosing 

 to form a series of chain-like links. CeUs transversely ellipsoid, divid- 

 ing in 2 planes and appearing in more than 1 series within the wide 

 gelatinous sheath. Cell wall in 2 saucer-shaped halves, adjoined in 

 the midregion, the line of juncture not always evident. Cells 7-10/a 

 in diameter, 3.5-5/x long. 



Very common in desmid habitats and soft water lakes. Mich., Wis. 



Published descriptions of this species do not mention the two-part 

 structure of the cell wall, a character of R. conjunctivum. Also the 

 shape of the cells in our specimens agrees closely with a plant which 

 W. and G. S. West originally described as R. apiculatum. The ar- 

 rangement of the cells and other features, the irregular form of the 

 filament in particular, justify referring our specimens to R. irregulare. 

 Radiofilum apiculatum West & West has been reduced to synonymy 

 with R. conjunctivum. The characteristics of our specimens would 

 apparently justify emending the description of R. irregulare if it 

 were determined that the type specimens possess the wall structure 

 of R. conjunctivum. 



Suborder Schizomeridineae 

 family schizomeridaceae 



In this family, which consists of the single genus Schizomeris, the 

 unbranched filamentous habit takes on a multiseriate expression. 

 The plant is uniseriate in the basal portion, where the cells are long 

 and cylindrical, but becomes multiseriate through cell division in 3 

 planes in the distal region, where the cells are brick-hke and quad- 

 rangular. The cross walls of the lower cells are thick plates. Chloro- 

 plasts are broad parietal bands which encircle about % of the cell 

 wall in the lower cylindrical cells, but become massive and com- 

 pletely fill the cells in the distal portion of the filament. 



The multiseriate habit and the method of zoospore escape (men- 

 tioned below) are characters which have influenced some phycol- 

 ogists to treat Schizomeris as a member of the Ulvaceae. It is an 

 enigmatic plant, and its inclusion with either the Ulotrichales or the 

 Ulvales seems justifiable. 



SCHIZOMERIS Kuetzing 1843, p. 247 

 Characters as described for the family. Filaments uniseriate below, 

 with cylindrical cells; multiseriate above, with brick-like cells. 

 Chloroplast a parietal plate nearly encircling the lower cells, with 



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