Thamnobryum confertum H. Robinson 1974

Thamnobryum confertum

Thamnobryum confertum (Mitt.) H. Robinson, Phytologia 29 (2):117, 1974.

Porotrichum confertum Mitt., Rep. Sc. Res. Voyage Challenger Bot. 1(4):81, 1885. [Original material: Mas a Tierra, coll. Moseley, 1875.]

Rather robust plants with secondary stems to 8 cm long, stipes to 3.5 cm long. Stipe leaves with squarrose-recurved tips. Main stems and branches densely foliate, scarcely compressed, densely branching with branches to 2 cm long. Main stem and branch leaves ca. 2.5 mm long, 1.0 mm wide, leaves of smaller branches 1.2 mm long, 0.4 mm wide, all leaves broadly ovate becoming narrowly oblong above, smaller leaves elliptical; lateral margins subentire, recurved below; apex acute, in branch leaves sharply dentate; costae stout throughout, ca. 50–60 μm wide at base, ending about 5–10 cells below apex, smooth abaxially; most cells of lamina 7–10 μm wide, slightly incrassate, upper cells 15–25 μm long, median cells mostly 20–35 μm long, a few basal cells to 50 μm long. Dioicous.

MAS AFUERA: Q. Casas, H. & E. 338b.

The species is endemic to Juan Fernandez. Bartram (1957) was doubtful of the validity of the species. On the basis of the new collection cited above, which shows Bartram’s key characters, I would think the species distinct. A difference from T. carolii not mentioned by Bartram is the thinner cell walls.