NO. 1 DAWSON: MARINE RED ALGAE OF PACIFIC MEXICO 33 



Callithamnion rigidum sp. no v. 



PI. 10, fig. 4-5 

 Thalli fruticulosi, ca. 1 cm. alt., axes multos ramosissimos per rhizoidea 

 multicellularia affixos habentes; axes principales ecorticati, ca. 100 /x diam. e 

 cellulis saepissime 1.5 plo longiores quam latae compositi, tres ordines ramorum 

 parum attenuatorum paululum rigidorum habentes, ramis ultimis diametro 

 ca. dimidiae partis axis principalis (40-50 /*), cellulis ubique ca. 1.2 plo 

 longioribus quam latae; rami maxima ex parte multifarii, supra saepissme 

 distichi, longe infra partem supremam cellulae ferentis plerumque orientes, 

 adaxiaiiter curvati, ramis ultimis admodum infra cacumina quasi reductis, 

 terminaliter, autem, obtusis; glandicellulae nullae; tetrasporangia adaxialia, 

 in ramis ultimis seriata sessiliaque, subspherica, cum involucro crasso ca. 

 60 n diam.; cystocarpi in axibus principalibus subterminales; spermatangia 

 non visa. 



Thalli tufted, about 1 cm. tall with numerous profusely branched 

 axes attached by multicellular rhizoids; principal axes ecorticate, about 

 100 jx in diam., of cells mostly 1.5 diameters long, with 3 orders of 

 little-attenuated, somewhat rigid branches, the ultimate ones about half 

 the diameter of the main axes (40-50 fi), the cells about 1.2 diameters 

 long throughout; branches mainly multifarious, tending to be distichous 

 above, usually arising well below the top of the bearing cell, adaxially 

 curved, the ultimate ones somewhat reduced just short of the tips, but 

 terminally blunt; gland cells absent; tetrasporangia adaxial, seriate and 

 sessile on the ultimate branches, subspherical, about 60 //, in diam. 

 including the thick envelope; cystocarps subterminal on principal axes; 

 spermatangia not seen. 



Type: Holotype is E. Y. Dawson 8576, Dec. 20-21, 1949, in Herb. 

 A. Hancock Foundation. An isotype slide is in Herb. Beaudette 

 Foundation. 



Type locality: Lowermost intertidal, 2.5 miles north of South 

 Bluff, Isla Guadalupe, Baja California, Mexico. 



Additional material: Cooper 514, March 7, 1947, Playa 

 Rosarita, Baja Calif. 



This species shows certain resemblances to Callithamnion rupicolum 

 Anders., but is ecorticate, essentially multifarious and lacks the recurved 

 branchlets. Two collections, however, are somewhat intermediate in the 

 last two characters. These, D. 5354, La Jolla, Calif., and D. 5570, Point 

 Fermin, San Pedro, Calif., are irregularly distichous and show here and 

 there a tendency toward recurved branchlets. 



Callithamnion rupicolum Ander. 

 PI. 11, fig. 1 

 Anderson, 1894, p. 360, figs. A-B; Collins, Holden & Setchell, Phyc. Bor.- 

 Amer. No. 1648; Smith, 1944, p. 319, pi. 81, fig. 3; Dawson, 1951, p. 53. 



Thalli tufted, mostly to 1 (2) cm. high, epiphytic or saxicolus, 

 attached by a felted base consisting of prostrate branches and rhizoids; 

 erect axes numerous, abundantly branched, uncorticated except by a 



