AN ACCOUNT OF THE SPECIES OF POLYSIPHONIA ON THE PACIFIC COAST OF NORTH AMERICA. I. OLIGOSIPHONIA

Abstract

12. Plants with 5-6 pericentral cells 13 12. Plants with 7 or more pericentral cells ...... 17 13. Plants somewhat corticated below P. guadalupensis S. & G. 13. Plants not corticated 14 14. Segments in main branches mostly less than half as long as wide ...... P. concinna sp. nov. 14. Segments in main branches mostly as long as broad or longer 15 15. Smaller branches widely divergent; pericentral cells mostly 5 ......... P. Marchantae S. & G. 15. Smaller branches not widely divergent; pericentral cells 5-6 .... 16 16. Branching frequent; trichoblasts or scar-cells occurring regularly one per segment P. Johnstonii S. & G. 16. Branching infrequent, 15-25 or more segments occurring between successive branches; trichoblasts and scar-cells occurring at irregular intervals P. homoia S. & G. 17. Plants fully corticated except for smaller branches; pericentral cells mostly 7 P. Brodiaei (Dillw.) Grev. 17. Plants without cortication 18 18. Branching strictly dichotomous; pericentral cells 20-24 P. dichotoma sp. nov. 18. Branching not strictly dichotomous; pericentral cells fewer 19 19. Trichoblasts wanting; main axes sparsely branched, except for numerous crowded and very short lateral branchlets P. Dictyurus J. Ag. 19. Trichoblasts usually abundant; main axes often considerably branched 20 20. Trichoblasts and scar-cells always occurring one segment distant and one-fourth spiral turn from each branch base 21 20. Trichoblasts and scar-cells rarely occurring in the described positions 22 21. Plants mostly under 2 cm. high P. iniconspicua sp. nov. 21. Plants commonly 10-20 cm. high.. P. paniculata Mont. 22. Plants rarely over 1 cm. high, epiphytic P. Hendryi Gardner 22. Plants usually over 2 cm. high, mostly saxicolous .. P. Collinsii sp. nov.