244 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 12 



GIGARTINA Stackhouse, 1809 



Plants foliar to bushy, firm fleshy, dark reddish purple, simple to 

 abundantly branched, the branches terete to compressed or foliar; struc- 

 turally showing a filamentous medulla surrounded by a cortex of anti- 

 clinal branched rows of small cells ; tetrapartite sporangia in immersed, 

 rather spreading sori, the sporangia developed from cells of the inner 

 cortex; cystocarps generally crowded in special laterally projecting fertile 

 nodules or branchlets, the fleshy pericarp eventually rupturing. 



KEY TO SPECIES 



1. Segments of the branching thallus terete G. serrata 



1. At least the broader segments of the thallus flat .... 2 



2. Plants very small, about 5 cm tall, only the broadest upper blades 

 markedly flat ; slender subfiliform teeth abundant G. leptorhynchus 



2. Plants much larger and more firm, in large part flat ... 3 



3. Main branches pseudodichotomously forked, flat above, con- 

 tracted below, the margins minutely and closely aculeate serrate, 

 the surface aculeate papillate above; lower portions moderately 

 pinnately branched, the divisions lanceolate . . . . G. armata 



3. Main branches elongate, abundantly pinnately branched, the di- 

 visions linear lanceolate ; throughout on margins and faces fimbri- 

 ate with abundant small proliferations G. Chauvinii 



Gigartina serrata Gardner 



Plants to 25 cm tall, stifiE and dull red in color, the axis naked below, 

 above irregularly dichotomously branched 3-5 times, cylindrical through- 

 out, 2-3 mm diam., the upper segments pinnately beset with short branch- 

 lets which in the fertile cystocarpic state become recurved and more or 

 less crowded. 



Gardner 1927, p. 334, pis. 60-62. 



These plants had less of a pinnate aspect and less elongate terminal 

 segments than Gardner illustrates. However, they were cystocarpic and 

 mostly well advanced to maturity. They do not resemble the regularly 

 bipinnate plants which Harvey (1853, p. 174, pi. 27, figs. C1-C3) refers 

 to G. canaliculata and are more consistently cylindrical than those which 

 Howe (1914, p. 100) refers to G. Lessonii (Bory) J. Agardh. The type 

 locality for G. serrata is Ensenada, Baja California, about 250 miles 

 farther north than I. Cerros. 



Mexico: Baja California, on rocks at South Bay, I. Cerros, no. 34- 

 635, 10 Mar. 1934. 



