The water exuded from leaves as a result of root pressure. Sometimes guttation is confused with dew, although the origin and appearance of the resulting drops are different. On grass, dew appears as many drops that cover the surface of the blade; dew forms by condensation from water vapor in the atmosphere. Guttation appears as a single large pendant drop at the tip of the blade; guttation forms by the extrusion of liquid water from the moist ground. Sometimes one is seen, sometimes the other, sometimes both. When a wet heiligenschein is seen on the grass it is mainly caused by dewdrops; when a rainbow is seen on the grass it is mainly caused by guttation drops. See also dewbow.