NO. 1 TAYLOR : PACIFIC MARINE ALGAE 303 



oped or giving rise to lateral prostrate branches; erect branches at first 

 arching strongly toward the tips of prostrate branches, 2-3-(5) mm high, 

 70-150 /A in diameter, simple or with a very few branches; trichoblasts 

 abundant toward the tips of erect branches, up to 650 fi long, closely and 

 repeatedly branched in a strictly dichotomous manner, arising one per 

 segment in a 1/4 to % spiral to the left, ultimately deciduous, leaving per- 

 sistent scar-cells ; tetrasporangia one per segment, 40-55 fx in diameter in 

 relatively long and slightly spiral series in the tips of the erect branches; 

 sexual organs unknown. 



Type, Howe 3478, tetrasporic, collected by M. A. Howe from coral 

 reefs at Whale Cay, Berry Is., Bahamas, Jan. 29, 1905. The type is in the 

 herbarium of the N. Y. Bot. Garden. Additional collections by Howe 

 from the Bahamas, from Bermuda Is., and from South Caicos, B. W. I., 

 all in the herbarium of the N. Y. Bot. Garden seem definitely the same 

 plant. All were labeled as Lophosiphonia obscura, but in spite of the habit 

 of Lophosiphonia^ these specimens are clearly excluded from that genus 

 by reason of the exogenous origin of all or nearly all branches. The speci- 

 men in Phyc. Bor.-Amer. no. 1892 from the Bahama Islands, distributed 

 as Lophosiphonia obscura, is probably P. Howei. 



Three collections from the Pacific Ocean are tentatively placed with 

 this species, although slightly more slender and sterile. A collection ( Univ. 

 California Herb. no. 237032) by W. A. Setchell from Tutuila Is., 

 Samoa, July 1920, has the same vegetative features as P. Howei. Two of 

 the Taylor collections, listed below, are placed with this species also. 



Panama: Bahia de Panama, forming small entangled growths on 

 rocks in quiet water near the anchorage, I. Taboga, no. 39-620, 2 May 

 1939. Colombia: Choco, a sparse growth on old wood, Bahia Cabita, 

 Cabo Corrientes, no. 34-497 A, 13 Feb. 1934. 



PTEROSIPHONIA Falkenberg, 1889 

 Plants with a rhizoidal base, or erect, complanate, alternately distich- 

 ously branched; axis polysiphonous, sometimes parenchymatously corti- 

 cated, compressed to flat ; branches by reason of the young branch initials 

 appearing aculeate-dentate at the margins ; tetrasporangia in longitudinal 

 series in the flat branches or marginal branchlets; cystocarps formed 

 laterally on upper branchlets, the pericarps ovoid, thick walled, ostiolate. 



KEY TO SPECIES 

 1. Base rhizomatous; remaining ecorticate throughout P. dendroidea 

 1. Erect throughout ; the main axes becoming corticated . P. Baileyi 



