The Stinking Sense It Makes

by Michael Rossman

        Today, I have a biological marvel to share in science class. My Stapelia nobilis has bloomed, for the first time in three years. I bear it joyfully to my fourth graders, carefully cradling the two-foot fall of its jointed stem to keep from snapping off the stemlets that curve up everywhere, like soft green fingers of some thornless cactus. Though this leafless succulent looks like many another to a casual glance, its flowers are a wonder, even in their size -- for the two buds swelling towards open are already as large as my fist.

        The third has already come and gone, after its two days of glory, leaving the wilted remains of its petals -- sharply-tapered triangles seven inches long, with purple markings on a fuzzy, yellow-green ground -- wrapped around the cup of its center. I carry the plant around the tables so that each student can inspect the flower in turn, telling them to first look at the black structures and white stuff in its center, and then to stick their noses in and take a good sniff.

        My first two students don’t get it -- not because they’re dumb, but because their minds are automatically geared to a program that blinds them to the evidence of their senses. Even in its wilted aftermath, the flower is weirdly gorgeous; everyone can see that I love it, and am enthusiastic about its smell. They sniff in turn, with faintly puzzled expressions. To each I say, “Pretty neat smell, hey?” And each says, “Yeah, it’s nice,” or something of the sort, before gladly yielding to the next.

        But doubt surfaces openly at the third turn, as Anne says, “I don’t like it?” in a tiny voice. “Are you sure?” I ask, in apparent disbelief. She is sure. “How come? What’s it like?” She can’t say.

        But it comes more easily to Seth, who wrinkles his nose in disgust the instant he puts it to the flower. “Hey!” I say happily, “you don’t like it?” “No way!” “How come?” He hesitates, looking for a better way to say it, and finally just blurts it out: “It smells like dog-poop!”

        With the ice of habit broken, the rest make their own appraisals. Two with stuffy noses don’t get the full hit; the others identify the smell variously as rotten fish, old socks, compost, and just plain poop. Their collective focus on smell becomes so intense that I have to keep reminding them also to look at the black triangles jutting up in the center, the bumpy mounds of white stuff piled among them, before taking their own whiffs of this deliciously nasty odor -- which even my first two students come to recognize as quite foul, on second sniff.

        After we’ve gone round the table, I put the plant in the center to preside, and sit back with them to review the basics, in order to decipher this remarkable conundrum of a blossom that smells like shit. I begin with the elemental question: Why is a flower? I ask three times before they get it, and begin to offer their scattered bits of understanding: pollen, the bees carry it, so you can make the seeds. I tug at the bits until they fall into a form that makes sense enough for ten-year-olds to grasp.

        Going way back, I tell them that plants made pollen before there were insects to carry it from one to another. “So how did they pass it along?” By the wind, they deduce. “And which plants now still do it the old way, who produces pollen without colorful flowers?” With his nose stuffy with hay-fever, Jonathan says triumphantly, “Grasses! And lots of trees!” We ponder it: no one has seen bright flowers on the grasses, the pines. A few recall seeing the delicate, pollen-rich structures of their dowdy male flowers; I tell the rest to go look at lawns.

        So why is a fancy flower? Fancy flowers are a deal between plants and certain kinds of animals, mainly insects, a contract that says, “You help me reproduce, I’ll feed you.” We sort the details out and arrange them. Honey has nothing to do with the matter, it’s just what bees make with their pay -- the sweet sugar-water called nectar that butterflies also sip, the rich energy-food that powers their flight. Every detail of flower is geared to this bargain. Its color and nice smell cry here! to the right passerby; its pattern directs the visitor to where the sweet stuff is secreted; its form is arranged to place pollen on the right part of the sipper, and to receive it in the right place from another visitor so decorated.

        Though I emphasize a few key facts, most of my students are somewhat familiar with most of these details, and have doubtless heard the whole spiel before. But being able to articulate one’s fuzzy knowledge is a strong criterion, and I rehearse the whole until their sense of the sense it makes is strong and explicit, before we turn back to our wilted wonder.

        It smells like feces, like rot. So is it summoning butterflies? No way! So who, then, who responds to this smell? They are quick to suggest: flies! I ask: does this answer make sense? They agree: it’s strongly plausible. They lean inward in circle, their answers and hypotheses dancing in quick voluntary, hot on the chase.

        “Now think about those black structures,” I tell them, opening the flabby petals wide again. Arranged on five spindly triangles, spanning over a foot, the violet decorative lines form the trace of a bull’s-eye, growing steadily denser from the edge to the center, shouting here! to the eye as loudly as the smell shouts this! to the nose. The pattern is so striking that it calls us to recognize its function, before we focus again on the ten glossy black triangles jutting from the center, like sharp watermelon seeds.

        “Are they its seeds?” ventures Seth. “Nope,” I say smugly. They stare, baffled. I coax them: “Come on, how come you can’t see it? It’s so obvious! It only took me four times watching it bloom, over seven years, to see it. It’s staring you right in the face. How come you can’t see it right away?” They consider it, still blankly. Anne starts, “Seeds…?” and several take their frustration out on her: “Seth already said that!”

        “The black things,” I say again, “what do they make you think of? It’s staring you in the face. Think of the smell, put it together.” Their tension stretches, grows. It’s always a gamble, pushing them this hard; often they just can’t, and I have to tell them. But they know me well enough not to be cowed, and more often they do come through. This time several get it almost simultaneously, and chime out: “Flies! They look like flies!”

        They do indeed. I ask who knows what a decoy is, and wince with sadness when no one raises a hand. These city kids, this age! A few do know vaguely, from reading, and brighten with recall when I explain: the pond, the shapes crafted of rushes or wood, the circling ducks, the lure, the take. But is this plant a predator? The concept of plants luring flies is hardly unfamiliar, for all know about carnivorous plants. We ponder the idea; but as all can see that there are no actual flies or carcasses stuck on the flower, it seems unlikely.

        So why is it summoning flies? We go back to basics again: Why does the fly respond, why does she come to dog-poop, to rotten meat? Not to feed, or only secondarily; but mainly to lay her eggs, because the smell announces the right food for her children. So why does she come to the flower? To find a good place for her kids. Look at all those other fake fly-mamas already clustered there! And what’s that between them, that fluffy white stuff? We look again, leaning over the table, until first one and then all grasp it: fly eggs! What mounds! There must be hundreds of the minute ovoids. A closer look with a strong lens shows some hatching already, the small white larvae slithering over each other. So how did they get there? My students deduce that they must have been laid yesterday, when the flower was fresh in bloom, in my home.

        We sit back to consider. The whole flower makes sense now, or almost. We still don’t grasp the function of the fuzzy hairs covering the petals. They look like they’d be hard to walk over, if you were small and had a lot of legs; maybe they serve to discourage idle traffic, directing visitors physically toward the center of business. And the idea that the flower might be carnivorous lingers, for the eggs look so nutritious. Though this succulent doesn’t come from a nutrient-starved bog like the Venus fly-traps do, might it not appreciate a rich snack?

        Even with this possibility, the flower’s main function seems clear. No other potential pollinators are visible or readily imaginable, and Stapelia’s pollen is too scanty to trust to the wind. If someone transports it, we’ve learned who. But what a reward! My students don’t get the full prize until I ask them to consider the baby fly larvae already emerging. What will happen to them? The kids puzzle it out: Will they eat the flower, the plant? But they’re supposed to eat poop, carrion. So then … they’ll starve!

        What a cruel trick! We think back to why is a flower? The basic deal is a harmonious partnership: the pollinator gets a vital reward for vital service. Cheat the bumblebee and what happens? No more pollinated clover. No nectar, no bumblebee; no bumblebee, no clover. The cheater pays a stiff price. So everywhere, or nearly, the deal is fair, in a world ablaze with blossom and flutter until we interfered.

        Seated around my deviant succulent, we consider its strategy. The simple wonder of its flower, the stinking sense it makes, yields to a deeper wonder: How can it get away with this? Everyone else has to pay their pollinators for service, or else. Why doesn’t this stink-flower have to pay for its cheating?

        My students prowl the question with their minds like flies exploring a fresh dung-heap, until they puzzle it out. If clover cheats the bumble-bee, bye-bye clover; if stink-flower cheats a few flies, so what? The world’s full of mammals, defecating and dying; there’s always something around for fly larvae to thrive in. If a few hundred starve in an occasional deviant bloom, who will notice the difference? There’ll be plenty of adult flies around to port pollen the next time this stinking star spreads near another of its kind.

        With this decipherment of truant strategy, we’re done, after I lead them to spell out the stark functional logic: You can’t get away with cheating your helpers, unless they have other means of support. And you can’t go too far even then, as they conclude when we consider how flies would fare in a world with lots of stink-flowers and few mammals.

        This whole sequence of inquiry has taken less than half an hour with sixteen nimble minds, leaving us equal time to probe another wonder. I repeat it four times during the day; though the wondrous bloom was as weakened in odor as in structure when I brought it in, by the last class my students’ noses still wrinkle convincingly. The two buds still bulging will open next week, as we admire their fresh glory, open the vent high above us to thin the stink, and wager when the first fly will show up.

[A Pedagogical Afterword]

        This deviant flower is wonderful both in itself, and in the way it illuminates the usual partnership of pollination. I’m sure that my students will remember Stapelia’s surprising smell, anchoring its perverse strategy in their imaginations. Whether they will retain a somewhat deeper grasp of normal pollination strategy, I can only wonder.

        At the least, they’ve learned no less than they would through rehearsing this strategy in any other, less-exotic context. But I think it likely also that this learning has been made more coherent by its function in our process. For they have been moved to grasp the normal paradigm not simply in itself or in the abstract, but concretely for the purpose of understanding another model, related but radically different. Whether they consciously appreciate the perspective this offers on both is less important than the fact of their success, which testifies to the consolidation of their grasp.

        In each realm of inquiry, such luminous, contrary pivots of understanding may be found, casting central features into sharp contrast in ways that lead learners to deeper grasp. Some are like my stink-flower, promising an illuminating demonstration that can be reproduced by any teacher willing to find the material (check a horticultural source specializing in succulents) and make the modest effort involved (water, wait for flower.) Others are transient and irreproducible, depending less on special materials than on particular circumstances and participants, and a mind prepared to recognize them. Using such contrary pivots involves an instinctive taste and a learned art, doubtless somewhat idiosyncratic for each practitioner. Their use amounts to a strategy, as perverse in its way as Stapelia’s and as fertile as genuine feces. I find it an exciting way of teaching.

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