Flora of North America species comparison

Although earlier treated as synonymous with the tropical American Trichomanes radicans Swartz, recent authors have agreed that Trichomanes boschianum is a distinct taxon endemic to eastern North America. It exists as fertile diploids and tetraploids with occasional sterile triploids. Diploid cytotypes are prevalent in western localities, and polyploids are more common to the east. Although occurring in climatically moderated habitats, most populations suffer heavy mortality from sporadic droughts. The plants are very slow to regrow, and many populations are currently but a fraction of their size of 20 years ago. They seldom show evidence of sexual reproduction although gametophyte colonies of this species may be found in the vicinity of fertile sporophytes. Identity of these gametophytes has been confirmed by enzyme electrophoresis, but most occurrences of independent Trichomanes gametophytes in the eastern United States have been shown by this method to be those of T. intricatum (D. R. Farrar 1985).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Trichomanes membranaceum resembles species of subg. Didymoglossum in its growth form and chromosome number, and it has been considered by some authors to be of that subgenus. Its marginal scales, absence of stellate hairs, and leaf blades 2 cell layers thick set it apart from other species of subg. Didymoglossum and all other American Trichomanes.

The single population reported from Harrison County, Mississippi, in 1929 (E. T. Wherry 1964) may be extirpated, and no other occurrences of Trichomanes membranaceum are currently known in the flora. Because it is a common and adaptable species of varied habitats throughout tropical America, occurrences along the Gulf Coast and in Florida are not unlikely.

(Discussion copyrighted by Flora of North America; reprinted with permission.)