NO. 1 DAWSON : MARINE RED ALGAE OF PACIFIC MEXICO 63 



when present and have been observed in three other collections whose 

 proliferous branching and tumid older fertile nodal characters, however, 

 make their identity unclear: Dawson 1511, Punta Santa Rosalia; D. 

 1575, 1594 Bahia Ositos, near Punta Maria. 



Ceramium procumbens Setch. & Gard. 

 PL 24, fig. 3-4; PI. 25, fig. 1-3 

 Setchell & Gardner 1924, p. 772, pi. 27, fig. 51-54; Dawson 1944. p. 

 318; Dawson 1950, p. 128; Dawson 1959, p. 30. 



Thalli microscopic, the primary axes prostrate, attached to the 

 host by short rhizoids, 1-3 mm. in extent; primary axes 45-90 [m in 

 diam., distichously branched, the ramuli at first parallel with the host, 

 often opposite, later somewhat erect and sparingly dichotomously 

 branched; cortication only at the nodes; tetrasporangial ramuli short, 

 clavate; tetrasporangia completely immersed, irregularly placed, 40 p. 

 broad, 50 fi long; cystocarps single or rarely 2-3 together, short-pedicel- 

 late, spherical, 50-60 [x in diam., arising near the ends of the ramuli, 

 the main ramulus being pushed aside and 1-3 very short ramuli develop- 

 ing around them ; spermatangia developing from a broad, swollen region 

 on short, specialized ramuli. 



Type: Ivan M. Johnston 27a, July, in Herb. California Academy 

 of Sciences (1364). 



Type locality: Epiphytic on Grateloupia prolongata, Isla 

 Partida, Gulf of California. 



Mexican distribution: Pacific Baja Calif. — D. 2763, 2800, Punta 

 Santa Rosalia, Gulf of Calif.— D. 1323, Bahia de Los Angeles; D. 1816. 

 Ensenada de San Francisco; D. 10992, Bahia San Carlos; D. 18653, 

 Isla Tortuga; D. 18726, 18728, Isla Ildefonso; D. 18785, Puerto 

 Escondido; D. 18865, Bahia Agua Verde. 



Ceramium recticorticum Daws. 

 PL 24, fig. 5-6 

 Dawson 1950, p. 124, pi. 3, fig. 23-24. 



Thalli epiphytic, 1.5-3.0 mm high, often densely tufted, attached 

 to the host by prostrate, basal parts of filaments bearing long rhizoids; 

 branching apparently alternate; filaments 50-60 ,u in diam. above, with 

 non-forcipate, slightly incurved apices, corticate only at the nodes; 

 cortical bands about 2/3 as long as broad, slightly tumid, consisting, 

 except at the upper margin, of more or less rectangular cells horizontally 

 elongated and arranged in about four definite horizontal and vertical 

 rows, these regular rows maintained and usually unmodified by 

 growth of enlargement below; internodes scarcely evident in uppermost 

 500 /.(, of branch tips, lengthening to 10-30 /x at somewhat lower levels, 

 and then elongating markedly to 300-400 /.i in the entangled, basal 

 filaments from which verticils of rhizoids arise at the nodes; tetraspor- 



