Staminate inflorescences of Arceuthobium pusillum (eastern dwarf mistletoe, Viscaceae) emerging from the branch of its black spruce host (Picea mariana, host needles ca. 1.0 cm long). Among all the mistletoes, Arceuthobium has the greatest economic impact on human activity because of the damage these parasites inflict on commercially important forest trees. Whereas traditional classification of these plants has proven difficult owing to extreme reduction and lost of morphological features, molecular characters have yielded a well-resolved phylogeny.