20 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



13. Monosporangia borne on secund branchlets . . . .14 

 14. Erect filaments 4-6 [x. in diameter . . A. pacificum 

 14. Erect filaments 8.0-9.5 fx in diameter . . A. variabile 

 15. Thalli endophytic in the blades of Porphyra . K. porphyrae 



15. Thalli attached by a single basal cell 16 



15. Thalli attached by a multicellular basal layer . . . .17 

 16. Branching mainly opposite . . . . K. crassipes 

 16. Branching secund or alternate . . . K. arcuata 

 17. Reproduction by monospores ; filaments 7-8 ju. in diameter; some 

 of cells scarcely longer than broad . . . K. secundata 

 17. Reproduction by monospores and tetraspores; filaments 5-7 /* 

 in diameter ; cells usually 2-4 times as long as broad 

 K. seriaspora 



Rhodochorton purpureum (Lightf.) Rosenvinge 



Rosenvinge, 1900, p. 75; Doty, 1947, p. 162; Papenfuss, 1945, p. 

 327. Byssus purpurea Lightf oot, 1777, p. 1000. Rhodochorton rothii 

 (Turt.) Nageli, as interpreted by Drew, 1928, p. 177; B^rgesen, 1902, 

 p. 390, figs. 61-65; Smith, 1944, p. 182, pi. 46, figs. 1-2. 



Thalli forming deep red velvety areas on shaded rocks at high tide 

 level, consisting of basal, creeping rhizoidal filaments and numerous 

 erect filaments to 2 mm. long or more; erect filaments simple or spar- 

 ingly and irregularly branched, 10-18 /x in diam., uniseriate, of cells 

 1.5-2.5 diameters long, uniform in diameter throughout or slightly 

 attenuated ; cells with a single reticulate, parietal chromatophore without 

 a pyrenoid (or the chromatophore broken up into small pieces) ; tetra- 

 sporangia terminal on the erect filaments, or on short, clustered branch- 

 lets at the tips of the erect filaments, ovoid, 16-21 fx wide, 20-23 /u. long. 



Type: Holotype not designated and whereabouts of original 

 material unknown to the writer. 



Type locality: "Upon the base of the Abbot MacKinnon's tomb 

 in the ruined Abbey at Y-Columb-Kill, Scotland." 



Mexican distribution: Pacific Baja Calif. — D. 9626, on shore 

 rocks, Isla San Martin, April; D. 10368, on walls of a sea cave, Punta 

 San Eugenio, Nov. This material is rather short, being mostly under 2 

 mm. long. The filaments are less branched and the tetrasporangia more 

 often terminal on the primary filaments than in the more luxuriant forms 

 usually collected. 



