Note that the coleoptile is often confused with a ligule.
The development of a coleoptile has two pre-conditions:
(a) the sheath is closed; and (b) the hyperphyll is unifacial.
Only in this case does the cotyledonary leaf margin form a
closed circle and can develop a tubular structure. Ligules
are outgrowths across the adaxial surface of a bifacial leaf
region. They occur in foliage leaves of adult plants in
monocots and in other angiosperms. The coleoptile in its
strict sense occurs only in cotyledons of monocots