Dendrolycopodium hickeyi
Dendrolycopodium hickeyi, synonym Lycopodium hickeyi, known as Hickey's tree club-moss or Pennsylvania clubmoss, is a North American species of clubmoss in the family Lycopodiaceae. It is native to eastern and Central Canada (from Newfoundland to Ontario with isolated populations in Saskatchewan) and the eastern and north-central United States (from Maine west to Minnesota and south as far as Tennessee and North Carolina). The genus "Dendrolycopodium" is accepted in the Pteridophyte Phylogeny Group classification of 2016 (PPG I), but not in other classifications, which submerge the genus in "Lycopodium". "Dendrolycopodium hickeyi" is very similar to "D.  obscurum" except for a few minor but consistent features: side shoots round rather than flat in cross section, leaves all the same size. The oldest name for the taxon is "Lycopodium obscurum" var. "isophyllum". In elevating the plants from varietal level to species level, Wagner et al. opted to forgo the common (but not mandatory) custom of using the old varietal epithet as the new species epithet. They chose instead the name "Lycopodium hickeyi" while acknowledging the old varietal name as synonym.