LIANE HANSEN, host:
For the past month on WEEKEND EDITION, we've been running a series to commemorate the 200th anniversary of the birth of Charles Darwin. We've looked into his childhood influences, traveled to England to explore British attitudes towards Darwin, and visited the University of Kansas to ask students whether their religious beliefs inhibit their study of the natural sciences.
Today, we stick our nose into a lovely bunch of orchids. These brilliant, flashy, sensual and sometimes graphic flowers fascinated Charles Darwin. In his book, "On the Various Contrivances by Which British and Foreign Orchids are Fertilised by Insects," he wrote: In my examination of orchids, hardly any fact has so much struck me as the endless diversity of structure for gaining the very same end, namely, the fertilization of one flower by the pollen of another.
To Charles Darwin, orchids were vivid examples of natural selection, and of mechanisms that develop over generations to best ensure the perpetuation of the species. The title of this year's annual orchid exhibition at the Smithsonian National Museum of Natural History is "Orchids Through Darwin's Eyes." Last week, several of the curators showed us some spectacular flowers.
Ms. SARAH HADEEN(ph) (Orchid Curator, Smithsonian Institution): Hi, my name is Sarah Hadeen. I'm one of the orchid curators of the Smithsonian Institution. And I also manage all the orchid collections management and databases. And I also do all the bar coding for the collection.
Ms. MELANIE PYLE (Horticulturist, Smithsonian Institution): Melanie Pyle, and I maintain the interior plants in the museums of the Smithsonian.
HANSEN: As we walked around the cases and plantings, Melanie tended to the orchids - gently plucking a yellow leaf here, arranging and propping up blossoms there, so visitors could see them. The space was filled from floor to ceiling with orchids of every color, size and type. They came out of the ground, clung to trees, and draped over canopies.
It was a feast for the eyes. The room was sweetly fragrant and slightly humid. Contrary to what you might have thought, orchids don't live only in the steamy tropics.
Ms. HADEEN: They grow in every part of the world except for Antarctica. So, they can either be terrestrial, epiphytic, depending on the climate and the conditions that it's living within. So, it can very easily be, say, a Lady Slipper that can overwinter in Minnesota's winters to something that grows in the tropics.
Ms. HADEEN: Epiphytic is an orchid that grows in the treetops, where it attaches to the bark or to the tree, and then the roots are given nutrition from birds that pass by. They're also given nutrition from what's ever in the air, and in the water and in the humidity.
HANSEN: Nutrition from birds, by the way, is the polite way of saying bird poop. At the bottom of these trees with the top flowers, there's a carpeting of terrestrial orchids. Here is a passage from an early version of "On the Origin of Species," where Charles Darwin wrote about the Coryanthes.
Unidentified Man (Actor): Crowds of large bumblebees visited the giant flowers of this orchid in the early morning. And in doing this, they frequently pushed each other into the bucket.
HANSEN: This flower is not in the Smithsonian's exhibition, but there is a Lady Slipper that comes pretty close. Sarah Hadeen pointed out the bottom petal of the blossom - it looks like a little bucket. She calls it a pooch.
Ms. HADEEN: And what happens is the pollinator actually falls inside the pooch and has to crawl its way out. Now, as it crawls out, it goes past the polinia, which then the insect picks up and carries to another plant, and it pollinates the plant. So, it's a very ingenious pollination mechanism.
HANSEN: Melanie Pyle.
Ms. PYLE: Polinia is part of the male orchid, or the male sexual reproduction parts, that is taken to the female reproduction parts of another orchid. It's essentially pieces of pollen.
HANSEN: Darwin theorized that the ingenious methods orchids developed to attract pollinators were highly visible examples of natural selection. Bees pollinate Lady Slippers. But orchids attract other pollinators, too.
Ms. HADEEN: Hummingbirds and bats, as well as ants, flies, beetles.
HANSEN: And, as Darwin discovered, moths.
Unidentified Man: I have just received such a boxful from Mr. Bateman, with the astounding Angraecum sesquipedalia, with a nectar a foot long. Good heavens, what insect can suck it? Charles Darwin, letter to Joseph Hooker, January 25th, 1862.
Ms. HADEEN: One of the most famous of all the orchids that I studied is the Angraecum, and it was a sesquipedalia, which was found in Madagascar. It has a very long spur. The Angraecum that Darwin himself talked about was about a foot and a half in length. And what Darwin postulated in his book was that there must be a pollinator that has a long enough proboscis to reach deep inside the nectar tube to gather that nectar and, in turn, pollinate the flower.
And it wasn't until about four years after he postulated this that the pollinator was itself found in Madagascar, which was a night-flying moth.
Ms. PYLE: Okay, here we have an orchid by the name of Epidendrum. And what plant do you think it looks like?
HANSEN: I mean, it looks like something that I sometimes see growing on the side of the road or something that people would have in their gardens. They're very small flowers. It's like a crown of flowers at the top of the stem and little orange. I mean, I'm blanking on names. I'm thinking Sweet William, but I know that's…
Ms. PYLE: Close. This orchid has evolved to mimic the flower of the butterfly weed. This variety of orchids grows in fields next to the butterfly weed. And the butterflies mistake it for being butterfly weed, and then will land on it and try to drink the nectar. And this orchid doesn't even have to produce nectar to attract it. So, it just gets pollinated automatically.
HANSEN: I hate to anthropomorphic, but it sounds like a pretty smart flower.
Ms. PYLE: Incredibly smart.
HANSEN: Is there another example we'd like to see? I mean, I feel I'm overwhelmed here with just beautiful, beautiful flowers.
Ms. HADEEN: Well, we have one of our panels here because we don't have the flower itself. This is a terrestrial orchid called Ophrys. It puts out a scent that a native bee is attracted to. So, the male bee comes to the flower and what happens is, it tries to mate with the flower because it thinks it's the female bee. It also looks like the bee, if you look at the flower carefully.
HANSEN: It does. There are two little things that look like wings, and then there's a red that looks like the body.
Ms. HADEEN: Exactly. So, through scent as well as the visuals of the flower itself, the male bee is drawn in and pollinates the flower, but gets nothing from the flower.
HANSEN: Sexual deceivers is what you call them.
Ms. HADEEN: Exactly.
HANSEN: Would you read the quotation here from Dr. Rod Peakall, who is an evolutionary biologist in Australia, at Australia National University.
Ms. HADEEN: I would love to. The males aren't too picky. Their strategy is hey, I'll go for anything that looks like a female because I can't afford not to. Perfect.
HANSEN: There's another one?
Ms. PYLE: There's another bee-pollinated orchid. The Oncidium varieties, which are also known as Dancing Ladies…
Unidentified Man: There is grandeur in this view of life. From so simple a beginning, endless forms most beautiful and most wonderful have been and are being evolved. Charles Darwin, "On the Origin of Species," 1859…
(Soundbite of museum)
HANSEN: On the leaf-green wall of this orchid exhibition, there are various quotations from Darwin. And one in particular, I'd like to read it for you - owing to the struggle for life, any variation, if it be in any degree profitable to an individual of any species, will tend to the preservation of that individual, and will generally be inherited by its offspring.
The offspring also will thus have a better chance of surviving. I have called this principle natural selection.
(Soundbite of music)
HANSEN: Darwin, "On the Origin of Species," published in 1859. Charles Darwin was born 200 years ago this month. The ideas contained within that book continue to amaze and fascinate us. You can see pictures of some of the orchids we saw at the Smithsonian's orchid exhibition. They're on our Web site, NPR.org.