562 University of California Publications in Botany [Vol. 8 



There has been considerable confusion as to this species which was 

 described by C. A. Agardh from specimens said to have been collected 

 at Unalaska by Chamisso. Our specimens were collected at Unalaska 

 and in general seem to answer definitely to the description and speci- 

 mens of Agardh. The fronds are nearly exactly cylindrical through- 

 out, the branching is almost entirely opposite and the branches 

 decrease in size gradually for each successive order of ramifications. 

 In habit, branching, and in structure, D. media is clearly related to 

 D. viridis, but is a more ample and a coarser plant. It is clearly 

 distinct in habit, branching and structure from any of the actdeata- 

 group. Cross-sections do not show the dense external palisade-layer 

 of cells of the D. aculeata^ and its allies. The variety tenuis is typically 

 a much more slender plant, but is, nevertheless, coarser and more rigid 

 than any of the forms of D. viridis. The variety seems to be more 

 southern in its range than the type of the species. 



2. Desmarestia pacifica S. and G. 



Fronds slightly compressed below, terete above, branching opposite 

 throughout, each succeeding order of branches much reduced in size ; 

 subterminal branches 5-8 cm. long, tapering upwards but very slightly, 

 clothed with many, mostly opposite, blunt, ultimate ramuli, 2-5 mm. 

 long ; axial filament 40-50ft diam., surrounded by two layers of larger 

 cylindrical to subcylindrical cells; cortical layer not definitely 

 delimited. 



Santa Catalina Island, southern California. 



Setchell and Gardner, Phyc. Cont., VII, 1924, p. 6. 



We have only a single and imperfect specimen upon which to base 

 this new species, but, while it closely resembles Desmarestia media, 

 each successive order, the branches of which do not taper appreciably 

 upwards, gives the plant a characteristic seemingly very distinct. 



3. Desmarestia farcta S. and G. 



Fronds cylindrical throughout, at least 5 dm. high ; branches long, 

 opposite throughout, not attenuated, blunt, of 3-4 orders, 0.5-1 mm. 

 diam. ; stipe and holdfast unknown ; primary cylinder composed of 

 cylindrical cells 20-25,/x diam. in the center of a distinct "stele" of 

 3-4 layers of larger cylindrical cells 35-45/x diam., these surrounded 

 by 2-3 layers of large colorless cells irregular in form, 100-125/x, diam., 



