Meesia Hedwig, 1801.

The genus Meesia locally includes two species recognized by the spreading to squarrose ovate-lanceolate leaves; and it includes a very different plant with ligulate leaves and a costa that fills 1/2-2/3 of the leaf base.

Key to Meesia Etc.

In this key we treat costate and acrocarpous mosses of wetland sites, often in bogs and fens. Median cells are rectangular and smooth. The costa ends near the leaf apex. The four species listed here are very different from one another in gametophytic characters but they are easily recognized by the very long seta which bears an asymmetrical, somewhat pyriform capsule with a long hypophysis. Perhaps the most strongly differentiating character throughout the Meesiaceae is the strongly reddened and numerous basal cells of the persistent axillary hairs (discussed under Leptobryum). At first glance Triquetrella californica might be mistaken for a Meesia, but the former has papillose cells whereas the latter has smooth cells.

Species included in this key are all in Meesiaceae:
Leptobryum pyriforme (Hedwig) Wilson
Meesia longiseta Hedwig
Meesia triquetra (Richter) Ångström
Meesia uliginosa Hedwig

A. Leaves not squarrose; costa about 1/3 of leaf base .....B
A. Leaves squarrose; costa less than 1/5 the width of the leaf base .....C

B. Leaves very narrowly linear-setaceous; margin plane .....Leptobryum: L. pyriforme
B. Leaves lingulate with margin strongly recurved throughout; stem without an hyaloderm .....Meesia uliginosa

C. Leaf margins entire or nearly so; plant obscurely tristichous .....Meesia longiseta
C. Leaf margins toothed to the base; plant strongly tristichous .....Meesia triquetra