In monocots, the situation is very different. The cotyledon
is partly inside and partly outside the seed, and/or
partly above and partly below ground. For instance, the
seed, including the haustorial part of the cotyledon, may
be buried, but a coleoptile is above ground and has photosynthetic
function. Thus, the terms epigeal and hypogeal
should generally be used only with respect to the position
of the seed relative to the soil surface. In the case of
epigeal germination, in dicotyledonous seedlings the seed
is raised by an elongating hypocotyl, and in monocots by
the cotyledon (Figs 2A–C, and 11C, D). The seedling
axis in monocots remains generally very short. In seed
plants other than monocots, the epicotyl may be long or
short in both epigeal and hypogeal germination (see de
Vogel, 1979). This implies that except for the hypocotyl,
no lengths of other axis segments should be part of a defi-
nition of the epigeal or hypogeal germination mode