Hmm, there was a sci-fi book about this where a billion years into the future plants have developed sentience and humans are given intelligence by symbiotic fun

Hmm, there was a sci-fi book about this where a billion years into the future plants have developed sentience and humans are given intelligence by symbiotic fungi. Found it: https://en.wikipedia.org/wiki/Hothouse_(novel) https://en.wikipedia.org/wiki/Hothouse_(novel)