What is the origin of 'sleep tight'?
Read moreOne of the mysteries of the English language finally explained.
In clubmosses and orchids, which grow in association with mycorrhiza: a tuberous body, with rhizoids, representing the embryonic plant and giving rise to primordial leaves.
Late 19th century; earliest use found in Frederic Bower (1855–1948), botanist. From proto- + corm, after French protocorme.