NO. 1 DAWSON : MARINE RED ALGAE OF PACIFIC MEXICO 15 



Additional material: D. 496, Bahia Bocochibampo, Sonora, 

 Feb. Only carposporic plants present. 



This species is similar both to Porphyra thuretii and to the Japanese 

 P. tenera, but is dioecious. From the several dioecious Japanese species it 

 differs in the number of carpospores and of spermatia. The prominently 

 ruffled and divided thallus and the light, dull color are also distinctive. 

 The plant was first recognized as an undescribed species by G. J. Hol- 

 lenberg in July 1945. 



Porphyra naiadum Anderson var. australis var. nov. 



Plate 14, fig. 2 



Ad forman typicam speciei, at sporis asexualibus tantum 4 in fasci- 

 culis singulis secundum formulam - , r > - >' sporis liberatis longitudine 



a b c 



duplis quam latitudine. 



Thalli epiphytic on Phyllospadix (or Zostera), usually 1-2 cm. tall, 

 purplish red in color, consisting of a few to many blades arising from a 

 small, hemispherical, multicellular base; blades broadly obovate, cuneate 

 to a stipe-like part at the base, monostromatic, 25-30 /x thick in vegeta- 

 tive parts, of cells 8-10 fi in diameter and 12-15 long (anticlinal dimen- 

 sion) ; chromatophore single, stellate; reproduction apparently only by 

 asexual spores, these at the margin of the thallus in adjoining packets of 

 four according to the formula -2 , ^, ~, 6-8 by 15-19 a in dimensions. 



a b c 



Type: Holotype is Dawson 216, Jan. 14, 1946, on sheet 4112 in 

 HAHF. 



Type locality : On Phyllospadix, 8 km. south of Punta Descanso, 

 Baja California, Mexico. 



Mexican distribution: Pacific Baja Calif. — Common on Phyl- 

 lospadix torreyi and P. scouleri at virtually all peninsular and island 

 stations (except Isla Guadalupe) to as far south as Isla Magdalena, at 

 all seasons. In Bahia de San Quintin it occurs on Zostera marina as well 

 as on Phyllospadix. 



Porphyra naiadum was described by Anderson (in Blankinship and 

 Keeler, 1892, p. 148) without designation of a type. He indicated that 

 the plant occurs both on Zostera and on Phyllospadix, but since only 

 Phyllospadix torreyi occurs at the Farallon Islands with which the 1892 

 report deals, it may be assumed that the epiphyte occurring on that plant 

 represents the type variety of the species. This variant was called by Hus 

 (1902) P. naiadum f. minor, and that growing on Zostera, P. naiadum 

 f. major. These may now be designated P. naiadum var. naiadum and P. 

 naiadum var. major Hus. 



