Perisperms

Part of speech: noun

Definitions

1. Nutritive tissue of a seed, formed from the nucellus and surrounding the embryo, found in plants such as the pepper and the water lily
2. Starchy reserve tissue that lies outside the embryo sac within certain seeds and feeds the developing plant during germination
3. Several seed storage layers derived from the nucellus that surround the embryo and supply nourishment to the young seedling

Etymology: "Perisperms" is the plural of "perisperm", a botanical term for a layer of tissue surrounding the embryo inside a seed. The singular came into English from French "périsperme", and the two parts of its making are both Greek. The prefix "peri-" means "around", and the second element is "sperm", from Greek "sperma", meaning "seed". Put together, the name describes exactly what the tissue is: a store of nourishment lying around the embryo, which the seed draws on as it germinates. The plural simply counts several such seeds or several species in which the tissue occurs, so a botanist writing about perisperms is comparing that nourishing layer across different plants. The word belongs to the vocabulary of plant anatomy, where "sperm" keeps its old sense of "seed" rather than the modern biological meaning.