I managed to snap a photograph of a flowering C. pontederiifolia many years ago:
I managed to get this species of cryptocoryne to flower under cultivation in my flower bed too with a mixture of Garden soil and 'Horti' soil:
It then developed into a fruit (syncarpium) for me, ugly and black in colour:
The flower bed was unfortunately heavily flooded one rainy day and when I poured away the water into the drain (along with lots of floating dirt), I saw this:
It was too late by then, I have already poured all the floating seeds (which I thought were dirt) into the drain..... sob sob.