82 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 26 



Mexican distribution: Pacific Baja Calif. — D. 2583, 2586 

 (Williams & Kenyon) Isla Cedros, 20 m.; D. 2565, 2621, 2605, 2596 

 (Williams & Kenyon), Laguna de Scammon, 4-6 m. 



Platysiphonia clevelandii differs from P. parva in that two pairs of 

 flanking cells, instead of one, border each sporangium in a tetrasporan- 

 gial branch; also that the two lowermost segments of a branch lack 

 flanking cells, while in P. parva only the basalmost segment lacks flank- 

 ing cells. 



Platysiphonia parva Silva & Clear] 

 PI. 39, fig. 2-3 

 Silva & Cleary 1954, p. 259, figs. 1-37. 



Thalli epiphytic, to 2 cm. tall, attached by rhizoids, consisting of 

 ligulate, acute or acuminate blades 125-200 p, broad branched dorsi- 

 ventrally from the center line of each blade; blades five cells broad, 

 composed of a central axial cell row surrounded by four pericentral cells, 

 each lateral pericentral cell flanked by two cells; base of branches 

 with only the basal cell segment lacking flanking cells; tetrasporangia 

 produced in ultimate blades in two longitudinal rows, by acropetal suc- 

 cession, one sporangium by each lateral pericentral cell bordered by two 

 flanking cells only, which to not divide vertically; cystocarps urceolate, 

 slightly asymmetrical, prominent, 225-445 p in diam., 260-500 p high; 

 spermatangia forming an elongated sorus on either side of the mid-line 

 of ultimate blades, arising from the pericentral cells. 



Type: Silva 5786, Jan 27, 1950, in Herb. University of California, 

 Berkeley. 



Type locality: Melpomene Cove, Isla Guadalupe. Baja California 



Mexican distribution: Pacific Baja Calif. — D. 4086, 4139 

 (Hubbs), Dec. 7, 1946, Melpomene Cove, Isla Guadalupe, 20-35 m.; D. 

 8228, 8408, south anchorage, Isla Guadalupe, 6-20 m. ; D. 8468 Melpo- 

 mene Cove, Isla Guadalupe, 80 m. 



This seems to be a Guadalupe Island endemic, for all of the speci- 

 mens of this genus from that locality are P. parva, while all those from 

 mainland Baja California localities are P. clevelandii. 



Taenioma perpusillum (J. Agardh) J. Agardh 

 PI. 37, fig. 1, PI. 47, fig. 3 

 J. Agardh 1863, p. 1257; Papenfuss 1944, p. 206, pi. 23, 24; Dawson 1944, 

 p. 324. Polysiphonia perpusilla J. Agardh 1948, p. 16. 



Thalli minute, epiphytic or saxicolous, 2-3 mm. high, consisting of 

 horizontally creeping, branched, cylindrical, ecorticate, polysiphonous 

 branches 130-150 p in diam., attached to the substrate by unicellular 

 rhizoids below and giving rise on the upper side to erect or ascending 

 branches; erect parts giving rise to alternate determinate branchlets 

 with short cylindrical base and flat, ligulate blades about 100 p. broad, 

 500-1000 p long, terminating in 1-3 long terminal hairs (luxuriant, 



