NO. 2 DAWSON : MARINE RED ALGAE OF PACIFIC MEXICO 285 



but reaching 2-3 cm. long, tapering somewhat to their bases, subacute; 

 segments usually flattened and ± uniform in width throughout, 0.6-1.0 

 mm. wide, 180-300 ju. thick; transection showing a cortex of anticlinal 

 rows of 3-4 small, pigmented, squarish cells up to 4 /a in diameter on the 

 outside, and 2-3 irregular inner layers of rotund cells to 12 ju. in dia- 

 meter ; medulla densely stuffed with intertwined filaments ; reproduction 

 not seen. 



Type: Holotype is Taylor 637, Mar. 10, 1934, on sheet 193 in 

 HAHF. 



Type locality: Bahia Sur, Isla Cedros, Baja California, Mexico. 



Mexican distribution: Pacific Baja Calif. — D. 9401, Islas San 

 Benito, May; D. 9798, 9789, Bahia Sur, Isla Cedros, Apr.; D. 9159, 

 Bahia Asuncion, Apr. ; D. 9287, Punta Entrada, Isla Magdalena, May. 



All of the specimens collected to date (between March 10 and May 

 8) are sterile. Some of them are obviously juvenile while others appear 

 to be near maturity. One may expect reproductive material to be obtain- 

 able during the summer months. 



Taylor described this plant as a form of Prionitis filiformis Kylin, 

 comparing it to specimens identified as that species from the same locality. 

 These specimens (Taylor 34-633) have now been recognized as Zanar- 

 dinula lanceolata (see above). Z. filiformis, as represented by topotype 

 examples from San Francisco, California, is an entirely different plant 

 with sparse, remote, dichotomous primary branching and very short, 

 determinate secondary branchlets. Z. delicatula is irregularly, densely 

 and bushily branched, and the secondary branchlets are relatively long. 



Apparently closely related to Zanardinula delicatula and perhaps 

 ultimately to be united with it are three collections of a somewhat larger 

 plant from Punta Baja and from Isla Magdalena. These plants have the 

 same slender proportions (0.8-1.3 mm. broad), the irregular primary 

 branching and approximate, indeterminate secondary pinnate branching. 

 Some of them are tetrasporic and up to 25 cm. high. Those which most 

 closely resemble the type of Z. delicatula are from upper littoral tide 

 pools at Punta Baja (D. 8893, Jan.). 



Zanardinula mexicana (Dawson) Dawson 

 PI. 24, fig. 70 



Dawson 1945b, p. 93; Dawson 1949, p. 246. Prionitis mexicana 

 Dawson 1944, p. 283, pi. 67, fig. 2. 



Thalli 8-25 cm. high, attached by a discoid holdfast up to 1 cm. 

 broad from which arise several to many slender, erect, branched axes; 

 erect axes ± percurrent, with sparse, irregular, primary branching. 



