Flacourtiaceae seems to exist only as a place to put genera without a real family. (Some descriptions list xylosma in the willow family.) The primary Hawaiian member is the tree xylosma, called "maua". It is primarily described as a leeward tree, but I've found a few populations of them in the wettest windward rainforests on Mauna Loa. They're also easy to find in kipuka puaulu in the volcano park, just a little ways off the loop trail. The wet forest version often lacks the red pigmentation that is highlighted in the description and photos of the leeward trees.