propagulum
/prəʊˈpaɡjʊl(ə)m/Botany
noun
A portion of a plant, lichen, etc., capable of giving rise to a new individual; specifically (a) (in a lichen) a fragment of the thallus capable of propagating the lichen.
Origin
Early 19th century; earliest use found in James Edward Smith (1759–1828), botanist. From scientific Latin propagulum from classical Latin propāgō shoot laid down in layering, runner + -ulum.