What is the origin of 'sleep tight'?
Read moreOne of the mysteries of the English language finally explained.
1Of an algal stem or filament: composed of a single strand of large elongated cells. Of an alga: having filaments of this kind.
2Of a pollen grain: producing a single pollen tube during germination. Of a pollen tube: single.
Mid 19th century; earliest use found in William Henry Harvey (1811–1866), botanist. From mono- + siphon + -ous.