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PASSION-FLOWERS

Passion-flower or Maypop, Passiflora incarnata
Passion-flower, or Maypop, Passiflora incarnata
Image by Ruth McMurtry of Kentucky

The above Passion-flower, shown at about twice its natural size, looks impossibly complex. However, structurally it has a lot in common with our Standard Blossom, as the picture below shows.

Passion-flower or Maypop, Passiflora incarnata, image by Ruth McMurtryThe anther and filament constitute the male stamen, with pollen emerging from the anthers. A pollen grain is placed onto the female stigma, it germinates and sends a tube carrying the male sex germ down through the style to an ovule inside the ovary. The ovary will ripen into an edible, yellow, lemon-sized fruit, and the ovules in the fruit will mature into seeds. In the topmost picture you can see that the flower appears to have ten whitish petals. If you look closely you can see that every other "petal" is a little more scoop-shaped and green-margined than the next. The green-margined ones are sepals and the flatter, whiter ones are petals. So, this is all exactly normal, as in our Standard Blossom.

Still, it must be admitted that passion-flowers have some extra items the Standard Blossom doesn't -- but, not many.

First, all the parts mentioned above are held above the lower parts on a special kind of stalk known as a gynophore. When the fruit develops it'll still have its stalk attached. This is a good way to distinguish passion-flower fruits from other kinds of lemon-sized, yellow fruits.

cross section of a passion-flower blossomAlso, maybe the most spectacular part of the flower as well as the most confusing are the many slender, white-and-purple items radiating out from the base of the gynophore. It just happens that in a few kinds of flowers a special kind of outgrowth develops on the blossom's lowest or central parts, where all the sepals, petals and sexual parts come together. The outgrowth is often known as a corona, or "crown." Daffodils have spectacular crowns -- the cup-like things rising in the blossoms' centers. Passion-flower crowns arise the same way, but instead of being cup-like are divided into many white-and-purple, hair-like items. You can guess that the passion-flower's much-divided crown helps direct a pollinator's attention to the center of the flower where pollination needs to be done.

In the above cross-section, note how the stigmas are held above the flower so that the arriving pollinator must brush against them to get to the nectar at the bottom, center of the flower. When that happens, pollen on the pollinator is trasnferred to the stigma, and thus the blossom is pollinated. When the pollinator has its nectar and flies upward from the bottom of the flower, it will brush past the downward-facing anthers and thus get a new load of pollen to be deposited on the stigmas of the next flower visited.

Therefore, all this bizarre-seeming anatomy makes perfect sense.

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