Thecaphora seminis-convolvuli Liro
(a seed smut fungus)

This smut may be found either by searching for flowers with swollen anthers, or by bursting the ripe capsules with your fingers, from late August onwards and looking for dark dusty spores. Beware that the large ripe seeds are black and when half-ripe they can look as though they are covered in dust, but a true infection will produce copious spore dust from large lesions on the seeds.

Infected host flowers stay open into the evening after uninfected flowers have closed for the night.