Polysiphonia nigrescens Hudson Dataset GBIF Backbone Taxonomy Rank SPECIES Classification kingdom Plantae phylum Rhodophyta class Florideophyceae order Ceramiales family Rhodomelaceae genus Polysiphonia species Polysiphonia nigrescens Name Homonyms Polysiphonia nigrescens (Hudson) Greville ex Harvey Polysiphonia nigrescens Hudson Polysiphonia nigrescens (Huds.) Grev.