Monographs Details: Macromitrium longifolium (Hook.) Brid.
Authority: Sharp, Aaron J., et al. 1994. The Moss Flora of Mexico. Part Two: Orthotrichales to Polytrichales. Mem. New York Bot. Gard. 69 (2)
Family:Orthotrichaceae
Discussion:

Fig. 474

M. longifolium (Hook.) Brid., Bryol. Univ. 1: 309. 1826.

Orthotrichum longifoliumHook., Musci Exot. 1: pl. 44. 1818.

Macromitrium homahcronC. Miill., Bull. Herb. Boissier5:197.1897.

Macromitrium cirrosum has smooth setae and smooth to slightly plicate capsules, while M . longifolium has papillose setae and strongly 8-plicate capsules. Gametophytically it is difficult to differentiate the two. Macromitrium longifolium tends to have longer, more slender leaves which are undulate, particularly when moist, and often glossy. Macromitrium cirrosum can also have these characters, but they are more pronounced in M . longifolium. Both ofthese species are large, irregularly branched, and differentiated from other Mexican species by long, slender leaves, entire basal margins, and tuberculate basal cells.

I see no distinct differences between M . homalocron and M . longifolium. The literature suggests differences in leaf undulation and seta length as well as calyptra hairiness, but I find no definite correlations.