26 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



branchlets mostly simple, narrowed to 4 jw. in diameter, of 2 or several 

 cells 1,5-2.0 diameters long; asexual reproduction by monospores; 

 sporangia mostly terminal on the short lateral branchlets, or sometimes 

 sessile, ovoid, 6-7 ju, in diameter, 10-11 ju, long. 



Type: Holotype is Davidson 218a-40, Jan. 27, 1940, on slides 026- 

 028 in HAHF. 



Type locality: Epiphytic on Gelidium, rocky shore of w^est side 

 of bay, Puerto Refugio, Isla Angel de la Guarda, Gulf of California, 

 Mexico. 



Acrochaetium sinicolum (Dawson) Papenfuss 

 Plate 12, fig. 1 



Papenfuss, 1945, p. 317. Rhodochorton sinicolum Dawson, 1944, p. 

 256, pi. 41, figs. 1-2. 



Thalli epiphytic, 300-500 [i high, attached by a single, much-enlarged 

 basal cell which may be embedded between the surface cells of the host; 

 basal cell giving rise to from one to several erect filamentous axes which 

 branch abundantly near their bases, less frequently above; branches 

 longer above, cylindrical throughout, not markedly attenuated, 4.0-5.6 p. 

 in diameter, of cells mostly 3-5 (6) diameters long; chromatophore 

 parietal ; reproduction both sexual and by asexual monospores ; mono- 

 sporangia borne terminally on usually 2-celled lateral secund branchlets, 

 11-14 ju, long, ovoid, the pedicel cell very much smaller in diameter; 

 antheridia in loose, terminal clusters on short, branching lateral branch- 

 lets, ellipsoidal, about 4.5 ju, long. 



Type: Holotype is Dawson 739-40, July 18, 1940 on slides 029, 

 032-033 in HAHF. 



Type locality: Epiphytic on Dictyota, rocky shore at Isla Tur- 

 ner, off Isla Tiburon, Sonora, Mexico. 



Acrochaetium sclnaiae Dawson 



Dawson, 1949a, p. 3-4, pi. 2, figs. 11-12. 



Thalli epiphytic on Scinaia and Gloiophloea, forming small patches 

 1-3 mm. in diameter, or becoming continuous, consisting of an irregular 

 group of basal cells creeping on the surface of the host and fixing them- 

 selves firmly on the utricles and in the cracks between; erect filaments 

 of 2-5 cells, rarely branched, usually under 30 ju, high, about 4 /j, in dia- 

 meter; chromatophore parietal; reproduction both sexual and by mono- 

 spores produced terminally on 1 -2-celled erect filaments. 



