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Development from flower to fruit

Catalpa speciosa (northern catalpa)

The stigma of the receptive flower can barely be seen sticking out over the top of the opening of the corolla (petals).  The ovary is hidden inside the corolla.   remain at the base of the flower.  

As the ovules inside develop into seeds, the ovary lengthens to many times its original size.  It is now much larger than the sepals, which can still be seen at the top of the developing fruit.

When mature, the fruit splits open, releasing the many small winged seeds. 

Paulownia tomentosa (princess-tree)

As in Catalpa, the ovary is hidden deep inside the corolla tube.

After pollination, the corolla falls off, exposing the ovary, stigma, and style.  

The ovary enlarges greatly and the style withers.  

The mature fruit splits down the sides, releasing its seeds.

Acer saccharum  (sugar maple)

The wind-pollinated flowers lack petals and are produced before the leaves.  The anthers and stigmas hang below the sepals.  

After pollination, the ovary expands beyond the sepals.  Wings begin to develop from the sides of the ovaries.  The remains of the stigma and style can be seen here.  Developing leaves are seen here.

The samaras (winged fruits) are nearly full sized by the time the leaves are developed. 

Mature fruits

Juglans nigra (black walnut)

The flowers are wind-pollinated. Female flowers have only tiny sepals, but have large and feathery stigmas.  The ovary is hidden inside an involucre.

After pollination, the ovary enlarges.

The fruit becomes large and round.  The involucre develops into a thick husk that does not split open.  

After the fruit falls to the ground, the husk decays to expose the hard nut inside.

Passiflora incarnata (purple passionflower)

The petals and stamens are organized in obvious whorls below the ovary.  The three long styles extend sideways from the top of the ovary. 

As the ovary of the pollinated flower enlarges, the petals and sepals wither. 

The ripe fruit is a berry.  

Inside the fruit are numerous seeds surrounded by a fleshy pulp.

Quercus phellos (willow oak)

The ovary of the female flowers is surrounded by a many-scaled involucre.  The withered stigma and style can be seen on these developing fruits.

As the ovary enlarges, it pushes out of the involucre, which remains as the "hat" on top of the fruit, an acorn.