Flora of North America species comparison

The small dark green plants of Ptychomitrium incurvum are unmistakable growing on rock, with their glossy leaves tightly crispate when dry. The leaves are shorter than in P. sinense and are straight when wet, not somewhat falcate at the tips as is common in P. sinense. Sporophytes are very common in this moss and the old sporophytes persist for a long time. Sterile colonies of P. incurvum can be very reminiscent of Weissia controversa, but Ptychomitrium is more glossy; its leaves have smooth cells and without the strongly involute margins of Weissia.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Ptychomitrium gardneri are robust glossy plants easy to recognize by their green to dark green color, serrate, acuminate leaves, and narrow lobes of the deeply divided calyptra. The lobes of dry mature calyptrae often spread outward like the spokes of a wheel. The leaves are much longer and more narrowly acuminate than those of the somewhat similar P. serratum; the ranges of the latter and of P. gardneri do not overlap.

(Discussion copyrighted by Flora of North America; reprinted with permission.)