1925 ] Setchell-Gardner: Melanophyceae 495 



Most specimens collected show only the unilocular zoosporangia, 

 but although gametangia have been seen in the majority of the species, 

 we have not detected them, as yet, with certainty in any of our west 

 coast specimens. 



Key to the Species 



1. Thallus loosely attached, free at the margin 5. R. fungiformis (p. 499) 



1. Thallus firmly attached, not free at the margin 2 



2. Thallus up to 2 mm. thick, 12 cm. diam 3 



2. Thallus less than 0.5 mm. thick, 5 cm. diam 4 



3. Paraphyses up to 130 M long 3. R. verrucosa (p. 497) 



3. Paraphyses up to 360 M long 4. R. hesperia (p. 498) 



4. Zoosporangia 80-95m long 2. R. californica (p. 497) 



4. Zoosporangia 60-70> long 1. R. clavata (p. 495) 



1. Ralfsia clavata (Carm.) Crouan 



Fronds flattened, crustaoeous, circular in outline at first, later 

 becoming more or less lobed, firmly applied to the substratum by the 

 whole lower surface with occasional rhizoids, 2-20 mm. diam., about 

 150ja thick ; zoosporangia narrowly ovoid to pyriform, distributed over 

 the whole upper surface of the frond except, near the margin, 40-60/x 

 long, 13-18/a broad, borne at the bases of the paraphyses ; gametangia 

 short, terminal on the erect filaments, pluriseriate, paraphyses 80-100/x 

 long. 12-15^ broad, slightly clavate; hairs unknown. 



Growing on rocks, wood, etc., in the upper sublittoral belt, and in 

 tide pools in the littoral belt. Unalaska Bay, Alaska. 



Crouan, Alg. mar. du Finistere, Fasc. 1, 1853, no. 56 (excl. 

 specim); Reinke, Atlas Meeresalg., 1889, pi. 6, figs. 14-20, Algen- 

 flora. 1889a, p. 48 ; Kuckuck, Bemerk. zur mar. Algenveg., 1894, p. 244. 

 fig. 14; Setchell and Gardner, Alg. N.W. Amer., 1903, p. 253. Myrio- 

 nema clavatum Harvey, Man. Brit. Alg., 1841, p. 124. Linkia clavata 

 Carmichael, MS., in W. J. Hooker, British Flora, vol. 2, 1833, p. 391. 



The measurements given above for the zoosporangia are taken from 

 Kuckuck {Joe. cit.) and from De-Toni (1895, p. 313). The material 

 from Unalaska cited above is scarcely mature but seems to come 

 within the range of measurements as given in the diagnosis above. 

 We are unable to harmonize the measurements given by Far low (1881 

 p. 88) for this species, with the material which we have examined from 

 the Atlantic coasts of America and Europe. His measurements for 

 the zoosporangia are 150-180/* long, and 60-70/x broad. These measure- 

 ments are larger than those given for any other species except for 

 R. hesperia S. and G. 



