NUCLEUS

(Lat.) Literally any thing round which matter has accumulated, or to which it is affixed. In Botany, it is used in various significations:— 1. The central fleshy pulpy ma of an ovule. '2. That part of a seed contained within the testa, and consisting of either the embryo and albumen, or of the embrj'o only. 3. In lichens, the disk of the shield, which contains the sporules and their cases. 4. In the language of the older botanists what is now termed by gardeners a clove j that is, the secondary bulb of a bulbous plant. Nucleus. In Astronomy, the solid part or body of a comet, as distinguished from its nebulosity. See Comet. [s. 844]