7. Plant endophytic in the walls of large algae (sometimes epiphytic 

 also), consisting of an irregularly branched filament or pseudo- 

 parenchymatous mass of cells which bear no setae - Entocladia 



7. Plant epiphytic or otherwise attached, not endophytic; 

 pseudoparenchymatous or discoid 8 



8. Thallus a compact disc of definite Hmitation, with colorless hairs 



arising from the outer sheath of the cells; filaments not evident Chaeiopeltis 



8. Thallus a flat, broad, epiphytic disc with filaments 



evident; cells without setae — . — - . 9 



9. Thallus a broad, epiphytic disc, several cells in thickness, with 

 filaments radiating from a common center; margins of the frond 

 definite; evanescent hairs sometimes present Pseudulvella 



9. Thallus an irregularly spreading epiphyte; filaments adjoined and 

 compactly arranged, not radiating from a common center; one cell 

 in thickness; setae lacking Protoderma 



STIGEOCLONIUM Kuetzing 1843, p. 253 

 A branched filament arising from a prostrate portion of a thallus, 

 which may be reduced to a pseudoparenchymatous mass of cells. In 

 some species the major portion of the plant spreads in loosely 

 branched, horizontal filaments; plant covered by a thin, scarcely evi- 

 dent, film of mucilage. Branches of first and second order either al- 

 ternate or opposite, and composed of cells scarcely smaller than 

 those of the main axis, ending in bluntly pointed or setiferous cells. 

 Chloroplast a parietal plate covering most of the cell wall, especially 

 in the cells of the branches; 1 to several pyrenoids. See Hazen ( 1902, 

 p. 193) on the taxonomy of this genus in the United States. 



Key to the Species 



1. Plants mostly prostrate and creeping; filaments 



with a few short vertical branches S. polijmorphum 



1. Plants mostly erect, branched filaments; horizontal 



portion of the thallus reduced 2 



2. Branching mostly alternate - 3 



2. Branching mostly opposite - — 7 



3. Walls of main axial cells 1.5-2.5-(4)At thick; branching very irregular, 

 with long and tapering, as well as short, arbuscular or rhizoidal 

 branches produced throughout the length of the main axis--S. pachydermwn 



3. Walls of main axial cells thinner; branching regular, the branches 

 gradually attenuated toward the apices - — - 4 



4. Plants short-tufted; apices of branches not tapering to 



setae but short-pointed - S. nanum 



4. Plants not short-tufted; branches elongate, gradually attenuate, 



and ending in long setae 5 



5. Plants slender, main axis less than 8^4 in diameter S. attenuatum 



5. Plants stouter, main axis 8-18/u in diameter - 6 



6. Branches nearly always few-celled and thorn-like, 8-1 l/i in 



diameter in the main axis S. stagnatile 



6. Branches elongate, thorn-like branches rare; cells 12-18/^ in 



diameter in the main axis. — S. subsecundum 



[114] 



