288 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 12 



Heterosiphonia erecta Gardner 



Gardner 1927, p. 99, pis. 20, 21 ; Gardner in Setchell & Gardner 

 1937, p. 84, pis. 21-23; Kylin 1941, p. 34. 



This Mexican material, unfortunately sterile, seems to represent an 

 intermediate degree of coarseness, being somewhat larger than Phyc. 

 Bor.-Amer. no. 146, but more delicate than, though quite as tall as, 

 Gardner's no. 2540. The Ecuadorean material is both small and delicate. 



Mexico: Baja California, probably washed ashore at Point Hughes 

 on Cabo San Lazaro, no. 34-593, 7 Mar. 1934. Ecuador: Guayas, 

 from the rocky southeast side of Pta. Santa Elena, Salinas, no. 34-468, 

 8 Feb. 1934. 



Rhodomelaceae 



Plants usually bushy, generally filamentous but sometimes membra- 

 nous expanded ; growth from an apical cell, the axial row surrounded by 

 pericentral cells and sometimes these in turn by a more or less irregular 

 cortex; sporangia from segments formed on the inner side of the peri- 

 central cells, tetrahedrally divided, the branches usually little modified, 

 but sometimes stichidiumlike ; spermatangial clusters developed from 

 trichoblast rudiments; carpogenic branches four celled, produced on a 

 pericentral cell associated with certain sterile groups and an auxiliary 

 formed after fertilization ; carpospores formed from the outer cells of the 

 gonimoblasts, which are borne on a large fusion cell, and discharged 

 through the ostiole of the prominent pericarp. 



KEY TO GENERA 



1. Thallus showing naked pericentral cells at least in the youngest 

 branchlets 3 



1. Thallus throughout with cortication obscuring the pericentral 

 cells 2 



2. Branchlets not particularly contracted at the base, the growing 



tip sunken Laurencia 



2. Branchlets markedly contracted at the base, the growing tip 

 generally projecting Chondria 



3. Minute creeping plants with well-defined rhizomatous axis and 

 simple or subsimple erect branchlets 9 



3. Much larger plants, erect or, if creeping, the erect branches not 

 simple 4 



