What type of category does Echium and Oxydendrum have in common?
Oxydendrum Sourwood or sorrel tree, Oxydendrum arboreum, is the sole species in the genus Oxydendrum, in the family Ericaceae. It is native to eastern North America, from southern Pennsylvania south to northwest Florida and west to southern Illinois; it is most common in the lower chain of the Appalachian Mountains. The tree is frequently seen as a component of oak-heath forests.
Oxymitra Oxymitra is the only genus in the liverwort family Oxymitraceae, in the order Marchantiales. The genus includes two or three species.