1917 Muenscherj Key to Phaeophyceae 251 



ARTIFICIAL KEY TO GENERA 



A. Plants filamentous, thread-like, usually much branched. 



B. Plants small, microscopic to about 4 dm. long; sporangia usually 

 present. 

 C. Filaments composed of 1 row of cells. 



D, Basal part of the plant consisting of branched filaments ; erect 

 filaments usually much branched. 

 E. plurilocular sporangia between the cells of the vegetative 

 filaments. 1. Pylaiella (p. 254) 



EE. Plurilocular sporangia at the ends of filaments. 



2. Ectocarpus (p. 255) 

 DD. Basal part of the plant consisting of a cellular disc or pad- 

 like mass ; erect filaments usually little or not branched ; spo- 

 rangia at the ends of the filaments. 3. Phycocelis (p. 256) 

 CC. Filaments composed of several rows of cells ; filaments forming a 

 dense tuft ; sporangia on short lateral branches. 



4. Sphacelaria (p. 257) 

 CCC. Filaments composed of many rows of cells forming a more or 

 less hollow much branched filament. 

 F. Filaments hollow ; sporangia in groups that form transverse lines. 



5. Striaria (p. 257) 



FF. Filaments solid above, hollow below; sporangia scattered or if 



in groups not in transverse lines. 6. Dictyosiphon (p. 258) 



BB. Plants large, 4 to 10 dm. or more long, with solid central axis, 



much branched, forming dense tufts ; sporangia seldom present. 



7. Desmarestia (p. 258) 

 AA. Plants not filamentous, not thread-like, branched or unbranched. 

 G. Plant not branched. 



H. Plant composed of a large blade with or without distinct stipe. 

 I. Plant with a distinct blade, holdfast, and stipe; usually about 1 

 meter or more long. 

 J. Blades with one or more longitudinal ribs. 

 K. Blade with one rib. 



L. Blade broad, crinkled, often perforated ; rib broad ; 

 stipe short. 8. Agarum (p. 259) 



LL. Blade broad, not crinkled, not perforated; rib broad; 

 stipe long. 9. Pleurophycus (p. 262) 



LLL. Blade narrow, not crinkled, not perforated; rib nar- 

 row ; stipe usually long. 



32. Alaria, without sporojihylls (p. 277) 

 KK. Blade with 3 to 5 ribs. 10. Cost'aria (p. 262) 



J.T. Blades without longitudinal ribs. 



M. Blade smooth or with 2 rows of cross folds. 



N. Stii)e erect; base of blade without hapteres ; blade often 

 with 2 rows of cross-folds. 11. Laminaria {yi. 262) 



