Polysiphonia nigrescens f. protensa J.Agardh, 1863 Dataset GBIF Backbone Taxonomy Rank FORM Classification kingdom Plantae phylum Rhodophyta class Florideophyceae order Ceramiales family Rhodomelaceae genus Vertebrata species Vertebrata spec Name Homonyms Polysiphonia nigrescens f. protensa J.Agardh, 1863