588 University of California Publications in Botany [Vol. 8 



The type and only species mentioned by Greville is D. foenicu- 

 laceus. The type locality is "Mona Island" (Isle of Man) (cf. 

 Dillenius, 1741, p. 16). 



Key to the Species 



1. Fronds relatively small and delicate, with opposite branching. . 1. D. tenuis (p. 588) 



1. Fronds more robust, chiefly with alternate branching 2 



2. Fronds with slender, attenuated branches 3 



2. Fronds with fewer, shorter, thicker, blunt branches 



4. D. hippuroides (p. 589) 



3. Hispid with slender, short ultimate branchlets 2. D. hispidus (p. 588) 



3. Not as above 3. D. foeniculaceus (p. 589) 



1. Dictyosiphon tenuis S. and G. 



Fronds very fragile and flaccid throughout, 5-10 cm. long, with 

 main axis percurrent and 225-250/x diam. ; branches opposite, of 3-4 

 orders, flagellif orm ; ultimate ramuli blunt, 40-50ju, diam. ; sporangia 

 scattered, completely submerged in the cortical tissue. 



Golofin Bay, Alaska. 



Setchell and Gardner, Phyc. Cont., VII, 1924, p. 10. Dictyosiphon 

 foeniculaceus f. americanus Setchell and Gardner, Alg. N.W. Amer., 

 1903, p. 248 (not of Collins). 



We have but a few specimens of this species upon which to base 

 the diagnosis. They were collected by Mr. E. C. McGregor in 1900. 

 The species is based principally upon the delicate character of the 

 fronds, the main axis being only about a quarter of a millimeter in 

 diameter, and upon the prevailing opposite branching, alternate 

 branching prevailing in the other species. Our plant is much more 

 slender than the plants referred by Collins to his f. americanus of 

 D. foeniculaceus which also lacks the regularly opposite branching. . 



2. Dictyosiphon hispidus Kjellm. 



Fronds delicate and flaccid, freely branched on all sides into several 

 relatively long, primary, flagelliform branches, these in turn irregu- 

 larly branched, all clothed with numerous, short, subulate or cylin- 

 drical, ultimate ramuli, tubular below, solid above ; olive brown in 

 color, darker on drying. 



Growing on Chordaria in the lower littoral belt. Orca, Alaska. 



Kjellman. Algenveg. Murm. Meer., 1877, p. 47, Spets. Thall. II, 

 1877a., p. 39, pi. 2, fig. 1. Dictyosiphon foeniculaceus Setchell and 

 Gardner, Alg. N.W. Amer., 1903, p. 248 (in part). 



