Calliergon orbicularicordatum
in H. G. A. Engler and K. Prantl, Nat. Pflanzenfam. 231[I,3]: 1037. 1909.
Plants medium-sized to large, brownish yellow. Stems unbranched or sparsely branched (few shoots seen); axillary hair apical cell elongate-rectangular to short-linear. Stem leaves broadly ovate or broadly ovate-cordate; costa single, 90–109 µm wide near base, ending shortly below apex; alar regions indistinctly delimited, broadly oblong to transversely triangular, from margins 65–80% distance to costa; proximal laminal cells to 2 times as wide as distal cells; medial cells to 18(–20) µm wide proximally, 40–126 × 7–12(–14) µm in distal 1/3–1/2. Sexual condition unknown. Spores unknown.
Habitat: Habitat unknown
Elevation: elevation unknown
Discussion
It is unclear whether Calliergon orbicularicordatum is an expression of another Calliergon species from unfavorable conditions or if it should be recognized as a distinct species. K. Karczmarz (1971) reported C. orbicularicordatum from Alaska, Greenland, and Svalbard, but the features he used to distinguish this taxon are unclear.
Selected References
None.