fungi
Ascaria - In Outlander Claire is looking for ascaria mushrooms when she first meets Geillis Duncan. I have been unable to find any mushrooms of that name. It may perhaps be a typo, and the mushrooms Claire was looking for may in fact have been muscaria, which would fit the description given in the book as they have scarlet caps (Outlander only, chapter 9)
Corpse-candle - Claire stumbles across the body of a dead soldier covered in a bright blue fungus which she recognises as corpse-candle (DIA, chapter 46) I don't know if this is a real fungus.
Puffball mushroom - when Jenny is heavily pregnant with Ian, Jamie tells her she looks like a puffball mushroom (V, chapter 5)
Shaggy-cap mushrooms - growing in the Highlands (Outlander, chapter 17)
Toadstools - Claire notes these grew in abundance around the tarns in the woods near Castle Leoch (Outlander only, chapter 9)
Yellow shelf fungus - Claire and Geillie gather this at Castle Leoch (Outlander, chapter 24)
Corpse-candle - Claire stumbles across the body of a dead soldier covered in a bright blue fungus which she recognises as corpse-candle (DIA, chapter 46) I don't know if this is a real fungus.
Puffball mushroom - when Jenny is heavily pregnant with Ian, Jamie tells her she looks like a puffball mushroom (V, chapter 5)
Shaggy-cap mushrooms - growing in the Highlands (Outlander, chapter 17)
Toadstools - Claire notes these grew in abundance around the tarns in the woods near Castle Leoch (Outlander only, chapter 9)
Yellow shelf fungus - Claire and Geillie gather this at Castle Leoch (Outlander, chapter 24)