What type of category does Echium and Oxydendrum have in common?
Echium Echium is a genus of 60 species of flowering plant in the family Boraginaceae.
Ophioglossum Ophioglossum, the adder's-tongue ferns, is a genus of about 25–30 species of ferns in the family Ophioglossaceae, of the order Ophioglossales. The name "Ophioglossum" comes from the Greek, and means "snake-tongue".