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.
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.
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.
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