Explanation

In hypogeal seed germination, the epicotyls elongates instead of hypocotyls. This keeps cotyledons inside soil surface or may bring them just above the soil surface but there they remain non-green, dry up gradually and fall off, eg, some seeds of dicots Pisum, Cicer, Cocos, Mangifera and most of monocot seeds$-$Zea mays, Oryza sativa.