NO. 1 DAWSON: MARINE RED ALGAE OF PACIFIC MEXICO 73 



D. 20242 (Neushal), Punta Hughes, 25 m.; D. 13401, Isla Magdalena; 

 D. 13293, Isla Margarita, 3 m. Gulf of Calif.— J). 163-40, Isla Tiburon; 

 D. 382-40, Bahia Tepoca, 22 m.; D. 43-40, 73-40, 21710, vicinity of 

 Guaymas. 



Taylor's Revillagigedo Archipelago specimen is sterile and of uncer- 

 tain identity. 



A plant occurs abundantly in Bahia San Quintin, Baja California, 

 that reaches a height of 8 cm. and produces late in the season (Novem- 

 ber-February) a large number of entangling rhizoids from the lower cells 

 (Fig. 2, Plate 29). Fertile material has not been found, and the 

 collections are referred here pending further study (D. 8719, 8729, 8775, 

 21621, 21638, 21681, 21668, 21747). Similar rhizoid-producing plants 

 are at hand from Bahia Topolobampo, Sinaloa (D. 10962) and Salina 

 Cruz, Oaxaca (D. 10754). 



Griffithsia tenuis C. Ag. 



PL 31, fig. 5-7 

 C. Agardhl828, p . 131; Tseng 1942, p. 106, fig. 1; Abbott 1946, p. 441, pi. 

 3, fig. 1-7; Dawson 1944, p. 315; Dawson 1949, p. 237; Dawson 1951, p. 54; 

 Dawson 1959, p. 32. 



Thalli forming loose tufts to 5 cm. high, attached to the substratum 

 by unicellular rhizoids from decumbent filaments; branching sparse, 

 irregular, subsecund, originating from the proximal ends of mother cells 

 near the basal walls; cells essentially cylindrical, 100-180 //. in diam., 

 4-6 times as long; apices commonly provided with whorls of deciduous 

 (dichotomous) hairs; tetrasporangia spherical, about 80 //, in diam. at 

 maturity, without involucral cells, whorled, 4-12 at each of 2-3 fertile, 

 subterminal nodes (about 3-4 cells below the tip), borne on a unicellular 

 pedicel 30-40 ^ in diam. and 1.5-2 diameters long; sexual plants not seen 

 (modified from Tseng) . 



Type: A collection by Ruchinger, probably in the Agardh 

 Herbarium, Lund, Sweden. 



Type locality : At Venice, in the Adriatic Sea. 

 Mexican distribution: Pacific Baja Calif. — D. 8155, 8158, 8619, 

 19301 (Hubbs), Isla Guadalupe; D. 2516 (Williams), Laguna de 

 Scammon; D. 6625, Bahia Magdalena. Gulf of Calif.— D. 169-40, Puerto 

 Refugio; D. 400-40, Isla Pond; D. 345-40, Punta Penasco; D. 145-40, 

 Isla Tiburon; D. 1768a, 21689, 21704, vie. of Guaymas; D. 7801, Bahia 

 Conception; D. 18644, Isla Tortuga; D. 18556, Isla San Pedro Nolasco; 

 D. 18667, Isla Carmen; D. 7153, Puerto Escondido; D. 10849, 

 Mazatlan; D. 10955, 10899, Bahia Topolobampo; D. 6958. Isla Espiritu 

 Santo. Guerrero — D. 21346, Isla Grande. 



Microcladia coulteri Harv. 



PI. 30, fig. 4-5 

 Harvey 1853, p. 209, pi. 33, fig. A; Dawson 1945, p. 67; Dawson 1949, 



