258 Puget Sound Marine Sta. Pub. Vol. 1, No. 25 



6. DICTYOSIPHON Greville 



1. DiCTYosiPHON Chordaria Arcsch. Phyc. Scand. p. 372^ pi. 8. Fig. 8 

 Plants filamentous, one to three dm. long ; much branched ; central 



filament and main branches usually more or less hollow below, solid above; 



sporangia scattered, not in groups forming transverse lines. 



Reported from Friday Harbor by Setchell and Gardner (14), p. 248, 



growing on rocks in the middle and lower littoral zone. 



7. DESMARESTIA Lamouroux 



Plants filamentous, compressed or much flattened, pinnately branched, 

 coriaceous or membranaceous, solid. Central strand or axis composed of 

 one or several rows of elongated cells surrounded by larger long cells and 

 smaller round cells ; cortical layer composed of somewhat rounded cells. 

 Tips of young branches ending in a delicate pinnately branched filament. 

 Reproduction very little known ; unilocular sporangia known only in some 

 species, developing directly from cortical cells. 



KEY TO SPECIES 



A. Branches much flattened, blade-like, with a midrib. 1. D. ligulata 



AA. Branches terete or compressed, not flattened. 2. D. aculeata 



1. Desmarestia ligulata (Lightf.) Lamour. Essai. p. 25. Fig. 10 



Plant 50 cm. to 3 meters long; holdfast a small disc; stipe short, 

 gradually widening into a central blade 5 to 100 cm. wide; branches oppo- 

 site, about as wide as the central blade, flattened, with a delicate vein in 

 the middle, somewhat serrate at edge, tapering toward both ends. 



This is a variable species, the species being less common than the 

 wider and larger form, D. ligulata f. herbacea, which is less branched but 

 has larger blades. 



Common on stones, shells and holdfasts of large kelps in the upper 

 sublittoral zone. 



2. Desmarestia aculeata (L.) Lamour. Essai. p. 25. Fig. 11 



Plant filamentous, five to twenty dm. long; filaments two to four mm. 

 in diameter, terete below, much compressed above; central part of main 

 axis and branches traversed by an articulated filament; stipe and main 

 branches long and narrow; branches usually alternate, sometimes opposite; 

 younger branches margined with tufts of delicate hairs which later fall off 

 and are replaced by two rows of spines. 



The younger plants are pale brown but older plants get darker. The 

 plants lose their brown color and turn green soon after they are removed 

 from salt water. 



