Four species of Streptopogon are new to Argentina. The Bolivian S. heterophyllus, the only species previously registered is excluded from the Argentinian flora, and a major range extension of the Mexican S. matudianus is presented. Treatment of all four taxa includes descriptions, illustrations and SEM micrographs of sporophytic characters.
Gertrudiella validinervis (Herz.)Broth. (Pottiaceae, Musci) is new record for the bryological flora of Argentina. Gertrudiella validinervis (Herz.) Broth. are plants with strong central strand and hyalodermis present in the stem; acute leaves with base sheathing, costa with one stereid band and a multilayered cylinder of thick-walled guide cells. Laminal cells are medially bulging ventrally and flat dorsally but marginally bulging on both sides in several rows. This monotypic genus is registered for the first time for Argentina. The original description is completed with sporophytic characters.
The genus Pyrrhobryum is represented by 2 species in Argentina: P. mnioides (Hook.) Manuel and P. spiniforme (Hedw.) Mitt. Pyrrhobryum mnioides is known from Tierra del Fuego to Río Negro and P. spiniforme from northeastern Argentina, in Misiones. The latter is recorded for the first time from northwestern Argentina. Ecological notes and specific macroscopic characters are included. A key for the identification of Argentinian species of Pyrrhobryum is provided.