An only child, Fries was first interested in flowering plants by his father, but at the age of 12 his attention was taken by fungi. Within five years he had a knowledge of more than 300 species, to which he gave names, and on going to Lund he was able to see the works of Persoon and other mycologists and to get the current names for some of his specimens.
Dictionary of the Fungi
Fries was ... a child prodigy who yet in his teens probably knew more about the fleshy fungi than anyone in the world except Persoon.
The modern microscope did not exist when he began his work, and, while showing how much can be done without it, he may too long have underrated its value. But he lived to see it confirm many conclusions which his insight foresaw, and solve riddles which he had pondered, but was unable to divine.
However, the beginner has to know Latin. Apparently, field guides in one's own language had yet to catch on...