Flavonoid compounds from 36 of the 38 known taxa of the genus Arceuthobium (dwarf mistletoes) were examined. The flavonoid chemistry of the genus is rather uniform, all taxa producing 3-O-glycosides of the flavonols quercetin and myricetin. No infraspecific chemical variation was encountered, and in those instances where subspecific taxa are recognized, their chemistry was uniform. At the subgeneric level, members of subgenus Arceuthobium synthesize primarily glucosides, whereas galactosides are more common in subgenus Vaginata. In two of the four Old World species of subgenus Arceuthobium (A. juniperi- procerae and A. oxycedri) only myricetin 3-O-glucoside was detected. There are no absolute flavonoid differences between subgenera, sections, or series. On the other hand, flavonoids are useful in several instances at the species level. In several cases, chemical data lend support to the recognition of species which in the past have been considered doubtfully distinct on the basis of morphology. © 1979 the New York Botanical Garden.
