Plants had an already intimate, fifty million year old relationship with mycorrhizal fungi before the first root burrowed into rock and soil. Without the cohesive presence of this fungi inside of plants which, at the time, were little more than puddles of green goo, the very structure of plants as we know them would not have occurred.

Mycorrhizal fungi actually taught plants how to make roots and all terrestrial life owes its existence to that didactic.