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Abstract
The developmental anatomy and morphology of the ovule and seed in several species
of Heliconia were investigated as part of an embryological study of the Heliconiaceae
and to provide a better understanding of their relationships with the other families
of the Zingiberales. Heliconia species have an ovule primordium with an outer integument
of both dermal and subdermal origin. The archesporial cell is divided into a megasporocyte
and a single parietal cell, which in turn are divided only anticlinally to form a
single parietal layer, disintegrating later during gametogenesis. The embryo sac was
fully developed prior to anthesis. In the developing seed, the endosperm was nuclear,
with wall formation in the globular stage; a nucellar pad was observed during embryo
development, but later became compressed. The ripe fruit contained seeds enveloped
by a lignified endocarp that formed the pyrenes, with each pyrene having an operculum
at the basal end; the embryo was considered to be differentiated. Most of these characteristics
are shared with other Zingiberales, although the derivation of the operculum from
the funicle and the formation of the main mechanical layer by the endocarp are unique
to the Heliconiaceae.