Monographs Details: Macromitrium dubium Schimp. ex Müll.Hal.
Authority: Buck, William R. 1990. Contributions to the moss flora of Guyana. Mem. New York Bot. Gard. 64: 184-196.
Family:Orthotrichaceae
Description:Distribution and Ecology - Upper Potaro River Region: Summit of Mt. Wokomung,05º05'N, 59º50W, 1650 m, very dense bromeliad-dominated savanna, epiphytic. Boom & Samuels9086, 9100.

Discussion:

This is the first report of this species from South America, although M . trichophyllum Mitt, may be the same or a closely related Andean species. Macromitrium dubium is characterized by slender leaves with long, thick-walled, porose ceUs throughout; the basal cells are smooth, not tuberculate. O f particular interest is the naked, cucuUate calyptra. This combination of characters seems ample justification for the erection of Macromitrium sect. Reverberatum Buck, sect. nov. A Macromitrio vero folii celluUs longis incrassatis porosis laevibus et calyptris cucuUatis nudis diversa. Type: M . dubium Schimp. ex C. Miill.

The Guyanese material is sUghtly different from the Lesser Antillean material. Specimens from St. Kitts (type) and Grenada (all other Lesser Antillean material seen so named is misdetermined) has leaf apices long and slenderly acuminate with percurrent costae. The collections from Guyana have a shorter, blunter apex with a subpercurrent costa. However, since this same variation is expressed in Ecuadorian populations of M . trichophyllum, it seems imprudent to accord it nomenclatural status here.

Distribution:Guyana South America|