FAMILY TRIBONEMATACEAE 



The filaments are unbranched, uniseriate and composed of more 

 or less cylindrical cells. There is basal-distal differentiation in young 

 filaments, which are attached by a stipe and an adhesive disc. In 

 nearly all forms the 2-piece construction of the cell wall is clearly 

 evident, the juncture of the pieces occurring at the midregion of the 

 cell. When the filaments fragment, the cells dissociate at the planes 

 of juncture with the result that H-shaped pieces are formed (as in 

 the genus Microspora in the Chlorophyta ) . There are 2 to several 

 parietal disc-like chromatophores. Reproduction as described for 

 the order. 



Key to the Genera 



Cells elongate-cylindric or slightly inflated, with overlapping of 



2 wall pieces clearly evident in all cells Tribonema 



Cells short-cylindric, never inflated; 2 wall pieces not in evidence 

 except as occasional thick H-shaped bands external 

 to the cell wall and usually brown Bumilleria 



BUMILLERIA Borzi 1894, p. 186 

 Filaments short, or long and entangled; composed of cylindrical, 

 thin- walled cells; duplex character of the wall and H-shaped pieces 

 seldom apparent except in cells liberating reproductive elements; 

 chromatophores 2-8, parietal, yellow-green discs, with pyrenoids 

 demonstrable in stained preparations. 



Bumilleria sicula Borzi 1894, p. 186 



PI. 96, Fig. 6 



Filaments (in our specimens) short, the ends showing H-shaped 



pieces; chromatophores 2-4 yellow-green parietal bodies with a 



metalhc lustre; cells 8-13-(20)/x in diameter, I1/2-2 diameters in 



length. 



Tychoplankter; in swamps and ponds. Mich., Wis. 



TRIBONEMA Derbes & Solier 1856, p. 1 

 Filaments composed of cylindrical (sometimes slightly swollen) 

 cells, the walls of which are constructed of 2 sections overlapping 

 in the midregion of the cell; cells forming H-shaped pieces when 

 fragmentation of the filament occurs; chromatophores disc-shaped, 

 light yellow-green, 2 to several in a cell, without pyrenoids. 



The characteristic overlapping of the two portions of the cell wall 

 is often distinguished with difficulty when living or filled cells are 

 examined, but is apparent in empty cells and at the ends of broken 

 filaments where one-half of a cell remains attached to the adjoining 

 cell of the filament, thus showing one-half of the H. 



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