472 University of California Publications in Botany [Vol. 8 



Growing- on the base of Viva sp. in the lower littoral belt. Sitka, 

 Alaska, to central California (Carmel Bay). 



Greville, Scot. Crypt. Flora, vol. 5, 1827, pi. 300; Harvey, Phyc. 

 Brit., vol. 3, 1851, pi. 280; Saunders, Alg. Harriman Exp., 1901, 

 p. 423, pi. 46, figs. 1, 2; Setchell and Gardner, Alg. N.W. Amer, 1903, 

 p. 249; Tilden, Amer. Alg. (Exsicc.), no. 350. Not Collins, Holden 

 and Setchell, Phyc. Bor.-Amer. (Exsicc), no. 1795 (a mixture of 

 several Myrionemataceae) . 



Myrionema strangulans Greville has been variously interpreted 

 and the name has frequently been placed as a synonym under M. 

 vulgare Thnret. In the attempt to determine the exact nature of 

 M. strangulans, specimens from Greville 's herbarium, from the western 

 isles of Scotland (but not from Appin, the technical type locality) 

 have been obtained (through the kindness of Professor Isaac Bayley 

 Balfour) and carefully studied. From these the description given 

 above has been drawn up. We find specimens on Viva which agree 

 with these Greville specimens in every detail, except that the zoo- 

 sporangia in our plants average slightly larger. 



22. Myrionema obscurum S. and G. 



Fronds microscopic, distributed more or less irregularly on the 

 surface of the host ; creeping filaments much branched, very compact 

 and contorted, forming a pseudoparenchymatous layer ; erect filaments 

 sparse, unbranched, 40-70/x high ; true hairs unknown ; cells of creep- 

 ing filaments extremely irregular in shape and size, 4.5-10/x diam. ; 

 cells of erect filaments cylindrical, 6.5-7.5/a diam., quadrate or nearly 

 so ; zoosporangia very numerous, sessile on the creeping filaments, 

 ovoid to broadly clavate, 45-65/x long, 18-30^ broad ; gametangia 

 unknown. 



Growing on the blade of Costaria costata. Moss Beach, San Mateo 

 County, California. 



Setchell and Gardner, Phyc. Cont. II, 1922, p. 346, pi. 32, fig. 6. 



Myrionema obscurum seems decidedly distinct from all other 

 species of the genus. It seems to be a near relative of M. strangulans 

 Grev. The basal layer is very compact, and adheres very firmly to 

 the host, following closely the irregularities on its surface. We are 

 unable to make out whether or not the epiphyte causes the death of the 

 cells of the host, which seems- to be quite frequent in all of the plants 

 we have observed. The creeping filaments push among the dead cells 

 of the host at times. The zoosporangia are numerous and all sessile. 



