 Morphological description using the presence of a cyathium (see section above) is consistent with nuclear and chloroplast DNA sequence data in testing of about 10% of its members.This testing supports inclusion of formerly other genera as being best placed in this single genus, including "Chamaesyce, Monadenium, Pedilanthus", and poinsettia ("E. pulcherrima").Genetic tests have shown that similar flower head structures or forms within the genus, might not mean close ancestry within the genus.