The genus Viscum L. (Viscaceae) with 150 species in the world was known in Iran only by V. album L.
subsp. album. The plants of Viscum are hemiparasites growing on various host trees such as
Crataegus sp., Parrotia persica and Pyrus sp. To investigate the range of morphological variation in
different populations of these subspecies authors conducted detailed morphological and
micromorphology studies. Furthermore, anatomical features of stem, leaf, petiole and fruit were
investigated in different populations of this taxon. The presence of calcium oxalate crystals and platelet
ornamentation of wax crystalloid structures on leaf surfaces were interesting features that could aid
separating one population distributed in Golestan forest (NE, Iran) from others. The ornamentations of
seed and fruit surface provide further evidence in recognizing this population as a separate taxon. The
seed surface in V. album subsp. album is smooth while wrinkled in the population from Golestan forest.
Furthermore, the fruit surfaces are smooth in the former, but furnished with platelet crystalloid
ornamentations in the latter. These micromorphological differences were associated with important
evidence from gross-morphology: the prophylls are two at the axils of each leave in V. album subsp.
album, but four in the population from Golestan forest. In conclusion, the results of the present study
suggest recognizing the population distributed in Golestan forest as a separate taxon rather at
subspecific level. A new subspecies is described for this new taxon: V. album subsp. golestanicum
Saeidi, Shahi and Golmohammadi.
Key words: Viscum album subsp. album, Viscaceae, calcium oxalate crystals, Iran.