Identification notes
Most Jungermannia / Solenostoma species have a bit of a reputation for being tricky to identify. Actually, they aren’t, but only if adequate material is collected to enable a confident identification to be made. Jungermannia pumila is one of these. Unless it is a species that you know well, attempts at identification are best reserved for plants which have perianths. Fortunately, if these are present (unfortunately much of the time they aren’t!) they are quite conspicuous.
J. pumila is one of the most likely species in this group to be encountered on boulders in wooded hill watercourses. A quick look at its perianth will show it to be free to its point of stem attachment, which simply means that it does not have bract-like structures (the perigynium) partially enclosing it. Below the perianth, several of the upper pairs of stem ‘leaves’ look inflated, as they are in fact bracts which contain the antheridia. This paroicous inflorescence separates J. pumila from J. atrovirens, which also has a free perianth but male reproductive structures are borne on separate shoots (dioicous). Solenostoma hyalinum also grows in the same habitats as J. pumila but does not have a free perianth – it is enclosed by a single pair of female bracts which obscure its lower half.
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