Striae that lean toward the central nodule, with the sternum as the origin. Convergent striae may occur throughout the valve, at the valve center, or at the valve apices. In contrast, striae are radiate, or divergent, if they lean away from the central nodule, with the sternum as the origin.
Barber, H.G. and Haworth, E.Y. (1981). Guide to the Morphology of the Diatom Frustule. Freshwater Biological Association, 112 pp.