Stigonema mesentericum Geitler 1925a, p. 184 

 PL 130, Fig. 4 



A gelatinous, cushion-like mass, composed of filaments with very 

 short, broad, irregularly developed branches in which series of glo- 

 bose or ovate cells are arranged without definite order; heterocysts 

 compressed globose, intercalary or lateral; cells 6-12/x in diameter; 

 sheath close, thick and lamellate, inclosing small groups of cells 

 which form irregular lobes from the main axis; filaments 25S5fi 

 wide. 



Tychoplankter; in semi-hard water lakes. Wis. 



Stigonema ocellatum ( Dillw. ) Thuret 1875, p. 380 

 [Incl. S. tomentosum ( Kuetz. ) Hieronymus 1895, p. 166] 



PI. 130, Figs. 5, 6 



Filaments forming brown tufts or cottony masses, with long, nar- 

 row and curved branches; trichomes partly uniseriate; heterocysts 

 mostly lateral; cells quadrate-globose to globose, with intercellular 

 connections, 20-30/x in diameter in the principal filament, each cell 

 inclosed by a conspicuous individual sheath which is either colorless 

 or brown; cell contents blue- or oHve-green to bright marine-green in 

 the young cells of the branches; sheath wide and lamellated, brown 

 in the older parts, colorless in the branches; filaments 35-45/;i wide. 



Stigonema ocellatum is a very common species, appearing in a 

 great variety of fresh-water and aerial habitats. It is often a con- 

 spicuous component of the algal flora in habitats where desmids 

 abound, forming brown wooly mats on and over submerged aquatics 

 such as the culms of Scirpus, Utricularia, decaying leaves, etc. 



This is the only common species of Stigonema which has but one 

 series of cells in the filament (rarely showing a double series for 

 short distances ) . 



Mich., Wis. 



Stigonema turfaceum (Berkeley) Cooke 1884, p. 272 



PI. 129, Fig. 5 



Filaments much-branched, forming dark-colored, cushion-like 

 masses, the branches about the same diameter as the principal 

 filaments, long and curved, with hormogonia produced distally; 

 trichomes of from 2-4 series of globose or much compressed- 

 globose cells which in the hormogonia are 12/^ in diameter; hetero- 

 cysts intercalary or lateral, much compressed; sheaths wide, lamel- 

 late and yellow-brown in age; filaments 27-37/x in diameter. 



Tychoplankter. Mich., Wis. 



[548] 



