1917] Gardner: New Pacific Coast Marine Algae I 391 



Petrocelis franciscana Setchell et Gardner sp. nov. 



Plate 33, fig. 1 



Petrocelis Middendorffii (Rupr.) Kjellman, Collins, Ilolden and 

 Setchell, Pli^'cotheea Boreal i- Americana, no. 900 (not Phyc. Bor.- 

 Amer., no. 1548) ; Tilden, American Algae, no. 202. The Petrocelis 

 Middendorffii (Kupr. ) Kjellman mentioned in Setchell and Gardner 

 (1903, p. 357) is probably correctly referred, altlioug-li the material 

 is sterile, making- its determination somewhat nncertain. 



Thallo cartilagineo-gelatinoso, pins minnsve orbiculariter expanso, 

 ad saxa arete adliaerente, brnnneo-rubro, siccitate nigro, 2-2.5 mm. 

 crasso; strato basali cellnlis maxime anastomosantibus composito, 

 filamenta verticalia parallela, in zonis anastomosantia parce ramosa 

 et parietibus crassis gelatinosisqne indnta produeenti; prntoplastis 

 in filamentis verticalibns 3-5. 5/x, diam., qnadratis ant 2.5- plo diametro 

 longioribus ; tetrasporangiis intercalaribus, zonam ab superficie ex- 

 terna 25 cellnlis distantem occnpantibns, singulis, sphericis ad angnste 

 ellipticis, 25-40ju, longis, 20-28ft latis; cystocarpis antheridiisque 

 adhnc ignotis. 



Thallns of firm gelatinons consistency, forming more or less cir- 

 cular expansions of indefinite size, closely adhering to rock, color, 

 dark brownish red, black when dr}^ 2-2.5 mm. thick ; thallns consists 

 of a basal layer of profuselj^ anastomosing cells from whicli arises a 

 much thicker layer of perpendicular filaments parallel with each 

 other, anastomosing in zones and slightly branched, having thick 

 gelatinous walls; protoplast in the perpendicular filaments 3.5-5/i. 

 diam., quadrate to 2.5 times as long ; tetrasporangia intercallary, occu- 

 pying a zone about 25 cells from the outer surface, varying from 

 spherical to narrowly elliptical, 25-40/a long, 20-28;li diam. ; cystocarps 

 and antheridia unknown ; plants perennial. 



Type specimen in the herbarium of the University of California, 

 no. 188973. The type locality is Fort Point, San Francisco, Cali- 

 fornia. 



Common in the upper littoral belt along the California coast. 



Petrocelis franrisediid is probably the most abuiulant and most 

 widel}'' distributed of all the rock-incrusting algae on our coast. It 

 has been known for many years under the name of Petrocelis Midden- 

 dorffii (Rupr.) Kjellman, because of its general resemblance to the 

 plant figured and described by Ruprccht in 1851 under Cruoria Mid- 

 dendorffii. The material of Ruprecht's C. Middendorffii was collected 

 in the Ochotsk Sea. His figure indicates that the specimens from 

 which he drew it were just beginning to form tetrasporangia, as none 

 of these show thc^ mature tetraspores formed. Tlie base of the plant, 

 as figured and described l)y Ruprecht, consists of rows of small, 

 closely set parencliyniatous cells, and the upper portion consists of 

 filaments more looseh- held together by gelatinous walls. These vege- 

 tative characters belong to the genus Petrocelis as now understood 



