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



Thalli saxicolous, 7-20 cm. high, consisting of several to many erect 

 fronds from a holdfast of a group of stolons ; primary branches about 1 

 mm. wide, compressed to about 320 ju, thick, giving rise to about 3 orders 

 of irregularly alternate or subopposite, distichous, compressed branches 

 decreasing in breadth to about 400 fx. in the ultimate order; branchlets 

 more or less geniculate at first, later standing at about 45° angles, nar- 

 rower and more nearly cylindrical at the base; transection showing a 

 medulla of mixed large and small cells (7-21 ju, in diameter) of granular 

 content ; rhizoidal filaments congested in the subcortex but also scattered 

 through the medulla ; cystocarps 800-900 fx. in diameter, usually solitary 

 on segments of compound fructiferous branches, the branch bearing the 

 first cystocarp usually developing fertile lateral ramuli below and be- 

 coming elongated and at times branched above the cystocarp; tetra- 

 sporangia borne in elongate-elliptical sori on the swollen, blunt ends of 

 the rather short, ultimate ramuli, commonly producing additional fertile 

 lateral ramuli below but not prolonged above; antheridia not seen in 

 Mexican material. 



Type: Holotype is Gardner, June 8, on sheet 93572 in the Her- 

 barium of the University of California, Berkeley. 



Type locality: Moss Beach, San Mateo County, Calif. 



Mexican distribution: Pacific Baja Calif. — D. 5302, Punta 

 Descanso, Sept. (tetrasporic) ; D. 50, Cabo Colnett, Jan. (cystocarpic). 



Some other collections from northern Baja California are seemingly 

 near Gelidimn purpurascens, but tend to have tetrasporangial branchlets 

 approaching the condition in G. papenfussii. In the absence of more ex- 

 tensive series of specimens including both sexual and asexual material, 

 these variants cannot satisfactorily be interpreted. Typical examples of 

 G. purpurascens are considerably more robust in lower parts than G. 

 pulchrum and tend to have more and longer lateral branches than that 

 species. The cystocarpic branchlets differ in being extended and branched 

 above and in having fertile branchlets arising from below the first formed 

 cystocarps. 



Gelidium johnstonii Setchell & Gardner 



Setchell & Gardner, 1924, p. 742, pi. 72, 73, 46 fig. a; Dawson, 

 1944, p. 260 ; Dawson, 1949, p. 233, 237. 



Thalli saxicolous, 5-12 cm. high, consisting of several erect fronds 

 arising from a holdfast of entangled, branched stolons with adherent 

 discs; erect parts flattened throughout, expanded above the short, stipi- 



