In the 1860s Simon Schwendener proposed that a lichen, which looks like one small plant, is a fungus and an alga living together, and the leading lichenologists of the day would not have it. He was right, and it took decades to be believed. The settlement was odd: the whole arrangement carries the fungus’s name, and the alga keeps a name of its own that the lichen never mentions. Then in 2016 Toby Spribille, puzzling over two Bryoria lichens that seemed to be the same fungus and the same alga, one yellow with a toxic acid and one brown without it, found yeast in the outer skin of them, and of lichens from six continents. Exactly what it does there is still being argued over. So the count went from one to two to possibly three, and the name never had to change, because it had never said how many.