Polysiphonia of Tropical Pacific — Hollenberg 
199 
Fig. 1. A, Polysiphonia dotyi, portion of a prostrate branch showing rhizoid in open connection with the 
pericentral cell and ornately digitate tip. B, Polysiphonia dotyi, apex of branch, showing trichoblasts and 
origin of young lateral in connection with a trichoblast (the shoot apex and the young lateral branch are 
stippled). C, Polysiphonia exilis, apex of branch. D, Polysiphonia howei, apex of prostrate branch with exo- 
genous laterals and rhizoids at distal end of pericental cells. E, Polysiphonia howei, showing multicellular tip 
of mature rhizoid. F and G, Polysiphonia tsudana, with young and older spermatangial stichidia. 
