A mixed occurrence of Hypnum lacunosum and H. cupressiforme provides evidence that the two are genetically distinct

Plants with Hypnum cupressiforme Hedw. and H. lacunosum (Brid.) Brid. appearance that were collected in direct association with a mixed collection of the two differed only in leaf length and leaf lamina cell length, besides differences in habit and overall size. These leaf characters belong to the few that potentially differentiate these taxa, and they were studied among 97 samples representing four different shoot types found within the morphological span of these taxa. Statistically significant differences were found among the four different plant types and mostly between the two taxa, as defined by overall plant appearance, in leaf lamina cell length (not between taxa), leaf length, and leaf lamina cell length corrected for leaf length. When leaf lamina cell length was corrected for leaf length, this increased the precision of cell length as a distinguishing character. The occurrence of many intermediates between plant types and a great overlap in measurements among plant types and taxa suggests that additional evidence independent from morphology is required to decide about the taxonomic treatment of H. lacunosum in relation to H. cupressiforme. The pseudoparaphyllia were studied in 15 specimens of each taxon, but their appearance showed too much overlap to safely distinguish the two.