velamen
Concise Oxford English Dictionary © 2008 Oxford University Press:
velamen /vɪˈleɪmən/
▶noun (pl. velamina /-mɪnə/) Botany an outer layer of empty cells in the aerial roots of epiphytic orchids and aroids.
– origin C19: from L., from velare ‘to cover’.
'velamen' also found in these Oxford entries:

