Hypocotyl

Portion of a germinating stem below the cotyledons; also called the CAULICLE (q.v.). Hypo crateriform. See SALVERFORM. Hypo crater i morpho us. See SALVERFORM. Hypocycloid. Curve traced by a point on the circumference of a circle rolling without slipping on the inside of another circle. Such curves are much used for the flanks of gear-teeth, or the parts inside the pitch circle. See GEAR-WHEELS and EPICYCLOID. A special case of interest is when the rolling circle has a diameter one-half that of the circle within which it rolls. The hypocycloid is in this case a straight line coinciding with a diameter of the larger circle.