1. The arrangement of some factor in layers or strata. Thus vegetation in a woodland consists of an upper layer, the tree canopy, and a lower layer of herbs at ground level, often with one or more intermediate layers of shrubs and saplings. Other factors, such as temperature and light, show stratification, this being especially important in the study of aquatic ecosystems.
2. The practice of placing seeds between layers of moist sand or peat and exposing them to low temperatures, usually simply by leaving them outside during the winter. The treatment is necessary for those seeds that require a period of chilling before they will germinate. It is thought that low temperatures may block the action of a germination inhibitor. Compare vernalization