The shoots of the passion flower at the very tips of each stem / branch. you can take softwood cuttings in early summer or semi-ripewood cuttings in late summer, you will need a 50:50 of peat and sand in a propagator with bottom heat at 25c (77f)
An easier method is to propergate by layering, peg the tips of low growing shoots into the soil in early autumn and hopefully some should take root by next spring. Good Luck T bird+