When I first attempted to meet the challenge of moss and liverwort species identification, I tried to apply similar methods to those I use in identifying unfamiliar flowering plants, that is to learn the characters of the higher-level taxa to which each species belongs.

Familiarity with flowering plant families is a good start to homing in on potential candidate species, and I assumed the same would be true of bryophytes and their higher-level taxa. I was informed by expert bryologists that this approach would not work for bryophytes, and that I'd just have to learn the species one by one.

Experience has shown me that the experts were right, indeed the British Bryological Society Field Guide doesn't mention families at all. The text does note the order to which each described species belongs, but that doesn't narrow the options down very much. In contrast, it's hard to envisage a credible flowering plant field guide that didn't name the families for all species covered.

The key reason for this difference is, I think, that for the most part the characters being used to identify bryophytes are details of the gametophyte which are, of course, exclusively vegetative features. And as with flowering plants, the vegetative organs tend to assume morphologies dependent more on habitat than on taxonomic position. Attempting to identify flowering plants by vegetative characters alone would present similar difficulties to that encountered in determining bryophyte species.