119. Gametangia (conjugating cells, PI. 74, Fig. 4) becoming filled 

 with lamellated pectic substances; zygospores cushion-like, com- 

 pressed spheroid, or quadrate - - Zygnemopsis 



119. Gametangia not becoming filled with pectic substances during 

 conjugation; zygospores globose, compressed globose, or ovate. 120 



120. Axial chloroplasts 2 definite stellate bodies in each cell; species 

 common- .....Zijgnema 



120. Axial chloroplast without radiating processes, sometimes bridged 



to form an apparent single, dumb-bell-shaped mass. Zygogonium 



121. Chloroplast a parietal ribbon or band (sometimes only slightly 

 twisted, or nearly straight); 1 to several such ribbons in a cell; 

 pyrenoids several to many at rather regular intervals Spirogyra 



( including Sirogonium ) 



121. Chloroplast an axial plate or a band, with 2 to several pyrenoids, 



or with none 1-^ 



122. Chloroplast without pyrenoids Mougeotiopsis 



122. Chloroplast with several pyrenoids 123 



123. Gametangia becoming filled with pectic substances during con- 

 jugation; granular residues absent in the gametangial cells; 



plants of slender proportions - Debarya 



123. Gametangia not becoming filled with pectic substances; granular 

 residues of the protoplast occurring in the conjugating cells; 



plants usually relatively stout -— Mougeotia 



124. Filament consisting of more than one series of cells, at least in 



a portion of its length - - — 125 



124. Filament consisting of a single series of cells - 126 



125. Plant uniseriate at the base, with cyhndrical cells, becoming 

 multiseriate above and composed of box-like or brick-like 



units compactly arranged Schizomeris 



125. Plant multiseriate, or uniseriate in part; a false filament com- 

 posed of loosely arranged globose cells in a gelatinous 



strand - Palmodictyon ( in part ) 



126. Chloroplast a parietal network covering the entire wall, sometimes 



very dense and difficult of determination, with many starch grains 127 



126. Chloroplast not covering entire wall; axial, or if parietal a 



folded plate, band, or meshwork 128 



127. Cells cylindrical, several to many times their diameter in length; 

 wall thick in most forms, lamellated, sometimes with short 

 rhizoidal branches Rhizoclonium (in part) 



127. Cells not cylindrical but slightly larger at the anterior end ( some- 

 times inconspicuously so), where 1 or more ring-like scars are 

 formed as a result of cell division (PI. 29, Fig. 1); enlarged 

 female cell conspicuous when plants are in reproductive con- 

 dition Oedogonium 



128. Chloroplast either a massive, axial body, or if parietal in the 



form of a band, plate, or ring not covering the wall-— -129 



128. Chloroplast parietal, massive and continuous, or a close or open 

 network (branched chain) covering the entire wall or nearly so 141 



129. Filament composed of long, coenocytic units in which ovate 

 chloroplasts or reticulate strands are arranged to form narrow, 

 parietal, ring-like bands that encircle the cell; sexual repro- 

 duction by eggs and antherozoids Sphaeroplea 



129. Filament not a series of long cylindrical coenocytes; chloroplast 



otherwise; sexual reproduction isogamous or by motile heterogametes-.lSO 



[581] 



