The ontogeny of the ovule and fleshy seed appendage in Homalanthus populifolius (Euphorbiaceae) were studied with the light microscope and SEM(Scanning Electron Microscope) and compared with the development of fleshy appendage of Passiflora citrina (Passifloraceae).The results showed that:(1)The micropyle type of H.populifolius is exostomatic.The fleshy seed appendage develops from the micropyle,which does not come from funiculus,should be called caruncula,not aril.(2)The micropyle type of Passiflora citrina is endostome.The fleshy seed appendage of P.citrina develops from funiculus and will cover the micropyle later.This is the aril.A detailed discussion between the caruncula and aril is presented.The model of caruncula and aril are set up and its biological significance is discussed.