Marsh clubmoss  (Lycopodiella inundata)

Genus: a category used in taxonomy, which is below 'family' and above 'species'. A genus tends to contain species that have characteristics in common. The genus forms the first part of a 'binomial' Latin species name; the second part is the specific name.
Spore: microscopic particles involved in both dispersal and reproduction. They comprise a single or group of unspecialised cells and do not contain an embryo, as do seeds.