We have a number of Dillenia species (the genus of the elephant apple or handipara from India, Dillenia indica) native to our forests. Some of it, like the katmon, are endemic (not seen in any other place). Dillenia suffruticosa, which is a small shrub, is also native here (as well as a few other Asian countries). I saw it growing in brushes and slopes in Laguna and Quezon. In the PAWB Workshop last November, Dr. Edwino Fernando showed pictures of another Dillenia, D. caulicarpa (or cauliflora? this is what I remember the name mentioned by Dr. Fernando mainly because they saw it with flower on the trunk, cauli in Latin means stem, flora is flower and carpa is fruit - so stem flower or stem fruit). He said it is endemic in Samar.
Some parts of the katmon are culturally used. The Bureau of Plant Industries website states that the fruit is sour but has a certain acid flavor. Though its flesh is not agreeably tasty, it is still used to alter fish taste and cooked to a jam. The bark is said to also yield a red dye for coloring. In the horticultural show, a participant stated that the fruit is grinded and mixed with gugo, tanglad and calamansi, used as hair perfume.