Hypogeal

Hypogeal, hypogean, hypogeic and hypogeous are biological terms describing an organism's activity below the soil surface.

In botany, a seed is described as showing hypogeal germination when the cotyledons of the germinating seed remain non-photosynthetic, inside the seed shell, and below ground. The converse, where the cotyledons expand, throw off the seed shell and become photosynthetic above the ground, is epigeal germination.