sclerotium
Concise Oxford English Dictionary © 2008 Oxford University Press:
sclerotium /sklɪəˈrəʊtɪəm, sklə-/
▶noun (pl. sclerotia /-tɪə/) Botany the hard dark resting body of certain fungi, consisting of a mass of hyphal threads.
– origin C19: mod. L., from Gk sklēros ‘hard’.
'sclerotium' also found in these Oxford entries:

