12 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



Erythrotrichia tetraseriata Gardner 



Plate 1, fig. 5 



Gardner, 1927, p. 240. 



Thalli epiphytic, to 5-15 mm. long, attached by the basal cell or by 

 short rhizoids from it, uniseriate for some distance above the base, be- 

 coming tetraseriate in upper parts by two successive longitudinal cell 

 divisions; uniseriate portion 18-25 /* in diameter; mature reproductive 

 upper parts 38-44 ju, in diameter; cells quadrate to slightly longer than 

 broad; chromatophores band-shaped, entire or at times split lengthwise. 



Type: Holotype not designated. Syntype examined: Mrs. H. D. 

 Johnston (no number), in Collins, Holden and Setchell, Phyc. Bor. 

 Amer. No. 782 (as Erythrotrichia investiens) , copy in HAHF. 



Type locality: Epiphytic on old leaves of Zostera marina van 

 latifolia, San Pedro, California. 



Mexican distribution: Pacific Baja Calif. — A few individual 

 filaments epiphytic on Sphacelaria, D. 9283, May, Punta Entrada, Isla 

 Magdalena, are probably referable to this species. 



Bangiaceae 



Key to the Mexican Genera and Species 



1. Thalli consisting of ± cylindrical filaments . . Bangia 2 

 1. Thalli complanate, membranous Porphyra 3 



2. Thalli multiseriate at the base, with short branchlets . . 

 B. enteromorphoides 



2. Thalli uniseriate at the base, unbranched 



B. f us co-pur pur ea 



3. Reproduction by antheridia and carposporangia ; plants usually 



saxicolous 4 



3. Reproduction by asexual spores only; plants epiphytic on Phyl- 



lospadix or Zostera P. naiadum 



4. Plants dioecious 5 



4. Plants monoecious 6 



5. Blades 1.0-3.5 cm. wide; carpospores in packets of 8; antheridia 



in packets of 64 P. hollenbergii 



5. Blades 0.3-1.2 cm. wide; carpospores in packets of 8; antheridia 



in packets of 128 P. pendula 



6. Carpospores in packets of 32; antheridia in packets of 128 

 P. perforata 



6. Carpospores in packets of 8; antheridia in packets of 64 

 P. thuretii 



