In between Oxydendrum and Polygonum which one has  about 220 species?
Polygonum Polygonum is a genus of about 220 species of flowering plant in the buckwheat and knotweed family Polygonaceae. Common names include knotweed, knotgrass, bistort, tearthumb, mile-a-minute, smartweed and several others. In the Middle English glossary of herbs "Alphita" ( 1400-1425), it was known as ars-smerte. There have been various opinions about how broadly the genus should be defined. For example, Buckwheat ("Fagopyrum esculentum") has sometimes been included in the genus as "Polygonum fagopyrum".
Ptychopetalum Ptychopetalum is a genus of two species of flowering plants in the family Olacaceae (not to be confused with the Oleaceae or olive family), native to the Amazon rainforest. The indigenous name for the genus is Muira Puama, "potency wood". The species are shrubs or small trees growing to about 14 feet in height. Its leaves are short-petioled, up to 3 inches in length and 2 inches in breadth light green on upper surface, dark brown on lower surface. The inflorescences consist of short axillary racemes of 4 to 6 flowers each. The root is strongly tough and fibrous, internally light brown with thin bark and broad wood, has a faint odor, and tastes slightly saline and acrid.