The Annonaceae are woody trees, shrubs and vines comprising
about 130 genera and 2,300 species. The leaves are simple, alternate, lack stipules, and
generally are distichously arranged in flat sprays. The flowers are bisexual and
actinomorphic, possessing 3 whorls of perianth with 3 segments in each whorl. The
elongated floral axis also bears many helically disposed stamens and several to many
simple pistils. All of the floral parts are distinct. The stamens are very short,
consisting of the fertile central anther portion, a distal pad of fleshy connective
tissue, and a short fleshy basal portion. The stamens are generally so tightly packed on
the receptacle that often only the fleshy connective tissue of each is exposed. The
pistils each have a superior ovary with one locule and 1-many parietal ovules. Sectioned
seeds reveal channels or partitions in the ruminate endosperm. The pistils generally
remain distinct and develop into berry-like fruits but sometimes they coalesce into
multiple fruits like the custard apple.
Each "thumbnail" image below is linked to a larger photograph.
|
|
Cananga odorata, ylang ylang. Note the distichous leaves in the
first photo. The perianth consists of 3 whorls with 3 appendages in
each whorl. The outer appendages or sepals are small by comparison
to the 2 inner whorls. However, they are persistent and readily
visible in the early fruiting stage depicted in the 3rd photo. In
this species the pistils remain distinct and the cluster of fruit at the
left in the 4th photo was derived from a single flower. |
|
|
Artabotrys hexapetalus, ylang ylang. Note three whorls of perianth, one of the
inner petals has been removed to reveal the numerous greenish stamens and the yellowish
pistils. |
|
|
Polyalthia suberosa. The trimerous nature of the perianth is apparent.
The carpels of the apocarpous gynoecium remain distinct into the fruiting
stage in this species. The
section through a seed reveals ruminate or compartmentalized endosperm and a small embryo.
|
 |
Annona cherimola, cherimoya |
|
Annona muricata, soursop. Small tree from tropical America with edible, dark
green, heart-shaped fruit covered with fleshy, curved, "prickles".
Each "prickle" corresponds to a pistil. The pistils are
initially distinct but coalesce during development of the aggregate
fruit. The pulp
makes a refreshing drink or "icee". The close-up of the flower reveals the inner
two whorls of trimerous perianth and hundreds of tightly packed stamens forming a
yellowish cup around the base of the central cluster of numerous tiny whitish pistils. |
 |
Annona squamosa, sugar apple |
|
|
Monodora myristica. Although the 3-merous condition of the
perianth that is typical for the family is seen in this species, the
gynoecium is exceptional in being syncarpous. |
