NO. 1 DAWSON : MARINE RED ALGAE OF PACIFIC MEXICO 115 



5. Segments 200-300 (400) fi in diameter ... 7. robusta 



5. Segments normally all 200 ju, in diam. or less .... 6 

 6. Branching more or less densely dichotomous above; inter- 

 nodes short; segments mostly 2-5 diameters long ... 7 

 6. Branching not densely dichotomous above; internodes long; 

 segments 6-11 diameters long ... 7. longiarthra 



7. Segments 120-150 (200) /a in diam.; tetrasporangial concep- 

 tacles seriate, the low^er ones supporting 1-4 others on succes- 

 sive forkings above /. mexicana 



7. Segments 60-120 fx in diam.; tetrasporangial conceptacles all 

 terminal, or at least not conspicuously or predominately seriate 

 J. tenella var. tenella 



Jania subpinnata sp. nov. 

 Plate 9, fig. 2 



Thallis epiphyticis, telam contextam confusam in hospite ad 5 mm. 

 crassam efficientibus; ramificatione primaria dichotoma; ramificatione 

 secundaria subopposita vel unilaterali frequente, a terminis distalibus 

 intergeniculorum maturorum; segmentis cylindricis, plerumque 90-100 

 II diametro, 3-5 diametris longis. 



Thalli epiphytic, forming a densely branched, confused, matted felt 

 to about 5 mm. thick over major portions of the host ; segments cylindri- 

 cal, (70) 90-100 (120) /i in diameter, 3-5 diameters long; primary 

 branching dichotomous, the angles mostly about 45°, but subopposite or 

 unilateral, distichous-pinnate branching frequent and often prominent; 

 pinnate branches arising secondarily from near the distal end of mature 

 intergenicula, often becoming regularly dichotomously branched them- 

 selves ; conceptacles not seen. 



Type: Holotype is Davrson 3459, Nov. 10-11, 1946, on sheet 

 54860 and in box 55045, including slide 1454 and vial 2191, in HAHF. 



Type locality : Epiphytic on Digenta simplex^ Bahia de La Paz, 

 Baja California, Mexico. 



The peculiar secondarily pinnate branching distinguishes this plant 

 readily from other species of Jania along the Pacific Coast. It provides 

 an exception to the strict dichotomous branching characteristic of the 

 genus, as similarly an exception to the strict pinnate branching of Coral- 

 Una is seen in C. janioides. Such pinnate branches in Jania are not 

 entirely unique, however, for as Rosenvinge (1917) indicates, they may 

 occur in Jania rubens. 



