390 Puget Sound Marine Sta. Pub. Vol. 1^ No. 31 



time. Not enough specimens have been collected to determine the maxi- 

 mum size, and it has not been collected when bearing the assimilating hairs. 

 So far as known, this species is distinguished by its extreme width in 

 proportion to length, by the abrupt rounding off of the base of the thallus, 

 and by a lack of branches. 



The following is a modification and extension of Muenscher's (18) 

 treatment of the genus : 



DESMARESTIA Lamour. 



Plants filamentous or conjpressed or merely much flattened to blade- 

 iike, pinnately branched, coriaceous or membranaceous, solid. Central 

 strand or axis composed of one or several rows of elongated cells surround- 

 ed 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 s^Jecies, developing directly from cortical 

 cells. 



KEY TO NORTH PACIFIC SPECIES 



A. Branches much flattened, blade-like, with a mid-rib. 



B. Blades narrow, gradually tapering at base, firm in texture ; plant 

 body comparatively small. D. ligulata 



BB. Blades up to 100 cm. broad, gradually tapering at base to a short 

 stipe, thin and easily torn when dry ; plant body very large. 



D. herhacea 

 BBB. Blades broad, abruptly rounding at base to a short stipe ; 

 branches few or none; plant body small. D. tahacoides 



AA. Branches terete or compressed, not flattened. 



C. Branches compressed, alternate, coriaceous, many arising adven- 

 titiously. D. aculeata 



CC. Branches terete, almost all opposite, cartilaginous. D. media 



The writer wishes to express her grateful acknowledgments to Mr. 

 W. L. C. Muenscher of Cornell University, Professor Josephine E. Tilden 

 of the University of Minnesota, and Dr. T. C. Frye, Director of the 

 Puget Sound IMarine Station. 



CITATIONS 



1. Agardh, C. A. Systema Algarum. 259-261. 1821. 



2. Agardh, J. G. Species, Genera et Ordines Algarum. 1: (2.1) 

 J 65-170. 18i8. 



3. Borgesen, F. Marine Algae, in Warming's Botany of the Fae- 

 roes. 2:444-445. 1903. 



