My Taxonomic Kingdom for a Gorse

Special thanks to Eldritch Eternity for help brainstorming this post.

Something is amiss in the dungeons. Things have learned to sprout mushrooms that ought to grow flowers - fungi do not exist.

From the AD&D 2nd Edition Monstrous Manual

Those of you who've read wikipedia might've noticed something by now: fungi are not plants - in fact fungi are closer to animals, evolutionarily speaking, and have their own taxonomic kingdom to boot.

Maybe they didn't have this scientific knowledge back in the '80s. I read a book some time ago about hymenopterans - that is, ants, bees, etc. - and it included termites as hymenopterans. To my white surprise I discovered later in life that termites are in fact much more closely related to cockroaches and mantises than those other bugs that live in hives and have queens and so on.

This is a classification that continued past AD&D 2nd Edition (I won't call it a misclassification, because that would make for a shorter, less interesting post). Here it is in 3rd Edition:

And again in 5th:

This suggests some things about the world, the implied setting, on the scale of deep time.

According to the Science, in reality fungi evolved as a distinct kingdom of life about 1.2-1.5 billion years ago - maybe even 2.4 billion years ago - apparently for plants it's like a billion years ago - wow. There's a sort of plant called the quillwort which has been around about 252 million years, reproduces through spores like fungus do, and lacks an elongated stem or vegetative leaves. Although it's still photosynthetic, it's about the closest plant I've managed to find to fungus, and so something like quillwort makes sense to me as the ancestor of D&D's plant-fungus (or plungus). The relative abundance of underground niches - in dungeons, the underdark, etc. - might have incentivized these proto-plungus ancestors to lose their pigmentation, their chlorophyll, turn to decomposing organic matter, and eventually develop into mobile, predatory, even sapient forms.

"But semiurge," you may be thinking, "semiurge you scamp, you wetbrained fuckwit, you're burying the lede here - what of the saprophytic plants, the plants that are decomposers like fungi are - wouldn't those make more sense as the plungus ancestor?" - to which I must respond: no. Another thing I've discovered reading wikipedia for this post is that saprophytic plants don't really exist - they're actually myco-heterotrophic plants, that is parasites on fungus rather than proper decomposers on their own - their existence requires the existence of fungus, and so they could not be the plungus ancestor.

Aquatic mushrooms are rare - there's like one, apparently: Psathyrella aquatica. This is because mushrooms need to take in oxygen, and apparently this is a lot easier for them to do from the air. In a D&D world we might expect to see quite a few more aquatic mushrooms - perhaps from some less-derived plungus species that retain their photosynthetic ability, able to produce their own oxygen underwater.

Fungal cell walls in reality are made from chitin - same stuff that makes up bug exoskeletons - whereas for plants it's cellulose. Maybe paper-making is more widespread from an earlier time if plungi can be more easily made into paper - with implications for the development of informational & cultural technologies.

No proper fungi might mean no psilocybin, no amanitas - psychedelic culture in D&D world might be relatively impoverished, or maybe peyote and ayahuasca pick up the slack. Stoned Ape theory is endangered.

In-world, why might this have become the case? Being D&D, it's not necessarily a totally naturalistic explanation. There is no deity of fungus, but there is a demon-queen: Zuggtmoy. Maybe fungus once existed as its own kingdom, a kingdom that would've lent Zuggtmoy tremendous power due to its omnipresence, and was eliminated from existence in some cosmic conflict - plants then filling in the ontological void.