In another forum, some creationist had posted that conundrum as a supposedly great difficulty for evolutionary biology.
However, there exist several species of
parasitic plants, many of which do not photosynthesize, and which often resemble fungi more than plants. However, they often continue to produce flowers and other features that get them recognized as plants;
Rafflesia produces some especially large ones. Though one might want to give one's Significant Other a super bouquet of these flowers, be warned that
Rafflesia flowers smell like rotting meat; they are pollinated by flies.
There is evidence that some protists and "fungi" have gone a similar route. Oomycetes or water molds are most closely related to diatoms and brown algae; they are essentially algae that have lost their chloroplasts. Likewise, apicomplexans like
Plasmodium and
Toxoplasma have "apicoplasts" that are vestigial chloroplasts that only make fatty acids and the like.
Animals have also gone the fungus-like route.
Sacculina carcini and other rhizocephalans ("root heads") are blob-shaped parasites that send tendrils into their hosts. However, they are really parasitic barnacles whose adults have abandoned barnacle-like features other than being attached to some substrate; their larvae are nauplius larvae that resemble other barnacle larvae -- larvae which seek out some suitable substrate on which to rest and become an adult.
A creationist may respond that that is really "degeneration" and not really evolution; but though parasites often subtract features, they also often gain adaptations that are helpful for their lifestyle.