80 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



median area, or commonly in older parts more densely grouped at the 

 lateral margins of the medulla, rarely extending into the subcortex; 

 sexual plants few; cystocarps unilateral, 500-600 ju, in diameter, solitary 

 on the distal part of a branchlet, with a single, rostrate ostiole ; antheri- 

 dial sori elongate elliptical, superficial in the middle of the distal portion 

 of a branchlet; tetrasporangial sori usually elongated, on terminal parts 

 of somewhat swollen branchlets. 



Type: Holotype is a collection by Mrs. E. Snyder, Jan. 1898, on 

 sheet 77876 in the Herbarium of the University of California, Berkeley. 

 Isotypes are represented under number 585 of Phycotheca Boreali- 

 Americana. 



Type locality: In tide pools, La Jolla, California. 



Mexican distribution: Pacific Baja Calif. — At many stations 

 at various seasons along the peninsular coast to Isla Magdalena; also at 

 Isla Guadalupe, Isla Cedros and Islas San Benito. Revillagigedo Archip. 

 — Howell 462, Isla Clarion, Mar. 



Comparison of a series of Pacific Baja California specimens of Ptero- 

 cladia pyramidale with type material of P. okamurai reveals no satis- 

 factory differences between them. The only character pointed out in the 

 original description which suggests a distinction is the relatively few 

 rhizoidal filaments of the medulla. A survey of a number of specimens of 

 undoubted P. pyramidale, however, indicates that the quantity of rhiz- 

 oidal filaments is a variable character and one which must be used with 

 caution in making specific distinctions. 



Taylor (1945) has identified a number of specimens from the Gala- 

 pagos Archipelago as Pterocladia okamurai and has described the forma 

 densa to represent plants with the abundant, slender, congested branch- 

 lets of upper parts. Plants bearing these more filiform, congested branch- 

 lets occur throughout the range of P. pyramidale in Mexico, and such 

 branchlets are so indiscriminately developed that a single plant may con- 

 sist of parts of contrasting size and branching-habit. It seems unwise to 

 attempt to maintain forma densa as a clearly distinguishable entity. 



Study of others of Taylor's Galapagos collections seems to show that 

 the type of Pterocladia robusta is only a more luxuriant, less abundantly 

 branched and somewhat broader example of the plant he identifies as P. 

 okamurai. Examples of P. pyramidale with similarly broad segments are 

 to be found along the California and Mexican coasts. 



Moore (1945) has pointed out the unsatisfactory status of the 

 Mexican Pterocladia okamurai S. & G., as well as the Japanese "P. 

 nana, P. tenuis and P. densa of Okamura who gives no very convincing 



