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.
History of Pachypodium The history of the genus Pachypodium as a scientific classification began in 1830, when the genus was first used in a taxonomical system by John D. Lindley, who placed a single species, "P. tuberosum", in it. Lindley believed that this species was identical with one identified in 1781 as "Echites succulenta", which would make "Pachypodium" a taxonomical synonym of "Echites".