Identification notes
As the name suggests, this liverwort is most commonly found growing over and amongst Sphagnum, but will also stray onto wet peat. It is relatively conspicuous for a bog liverwort, having worm-like stems up to 3mm across and often forms small patches. Sometimes there is an orange-brown tint to the leaves.The leaves are orbicular and usually imbricate and obliquely inserted, giving a characteristic compressed appearance at the shoot tip. The stems appear little branched because the branches emerge out of view on the underside of the stems. Like other members of the genus it possesses flagellae; slender and virtually leafless pale green branches that emerge from the postical surface of the stem and are almost always present. These are absent in other genera with orbicular leaves such as the rare Biantheridion undulifolia.
The leaves of O.sphagni are bordered with 1-2 rows of thick walls cells giving a margin that is visible with a x20 hand lens. This is absent from other members of the genus. O.denudatum usually has abundant gemmae, which are absent from O.sphagni, and it doesn’t tend to grow on live Sphagnum.
Jungermannia gracillima also has orbicular leaves with a border, but this is made up of large cells and the stems lack the small underleaves that are present in Odontoschisma species
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