Ray (Composite flower the outer)

Collier's New Encyclopedia (1921)

of a composite flower, the outer or circumferential whorl of florets, as distinguished from those of the disk. In many composites the former are ligulate and the latter tubular. Medullary rays are vertical plates radiating from the pith to the bark through the wood of exogenous stems. In the cross section, the medullary rays constitute fine radiating lines; in a longitudinal section, they impart to the wood a satiny luster, which in the plane, the sycamore, etc., is so marked as to be highly beautiful. The medullary rays maintain a connection between the bark and the central part of a stem. Carpenters call medullary rays the silver grain. In ichthyology, one of the radiating, bony rods serving to support the fins. They are of three kinds; (1) Simple; (2) Articulated (showing more or less numerous joints); and (3) Branched (dichotomically split, the joints increasing in number toward the extremity). The differences in the character of the rays in the dorsal fin are an important factor in classification. In optics, etc., a line of light proceeding from a radiant point, or a point of reflection. A collection of rays is called a pencil. An incident ray entering a doubly-refracting crystal is resolved into two, called from their properties an ordinary and an extraordinary ray. The term ray is used also of one of the component elements of light, as the violet rays of the spectrum; or the luminous, actinic, or heat rays: Visual ray, in perspective, a straight line drawn through the eye.