Today I’ll talk about the structure of a Dandelion and tomorrow I’ll get into the freaky world of Dandelion reproduction and genetics. Then the day after (hopefully) I’ll get into the natural history of dandelions in
Dandelions look obviously different from the flowers I’ve highlighted up till now. And that’s because dandelions are composite flowers. An ordinary, non-composite flower typically has the standard physical structure I described when talking about Glacier lilies- a single pistil, surrounded by several stamens, surrounded, by petals surrounded by sepals… But a composite flower has not one, but multiple little flowers growing out of the same head. So when you look at a Dandelion or a Sunflower or a Black-Eyed Susan, you’re not looking at just one flower, but rather at dozens or even hundreds of miniaturized flowers.
3- Flowers composed only of ray flowers, which includes of course, Dandelions.
Composite flowers have a couple of other structural developments in common. Specifically, their miniaturized flowers (whether disk or ray) always have either 4 or 5 stamens (male parts), and the anthers of these stamens are actually fused together to form a cylinder around the style (central column) of the pistil (female part). The style passes up through the anther-cylinder and is topped by 2 stigmas. The ovule itself is located way, way down below the petals and sepals of the miniaturized flower, not in the center of them, as in the Standard Blossom.
Dandelions have a pollination/dispersal methodology that is the converse of the Blackbrush schema I described last week. Where Blackbrush is wind-pollinated and its seeds agent (usually rodent)-dispersed, Dandelions are agent (usually Bumblebee)-pollinated, and- as every schoolchild knows- wind-dispersed. The parachutes of Dandelion seeds are actually the sepals of the miniaturized flowers, which following fertilization dry up and remain attached to the new seed, allowing it to be blown afar.
Tangent: Over the past week I’ve been building a back-up mountain bike in my garage. (Long-story short: I had a 9-year Titanium frame from an older bike that developed a crack, was rebuilt under warranty, and I collected “modern” parts from various sources to build up a nice, light stiff back-up bike, for the next time the frame on my primary bike breaks- which it inevitably will.) In the final cabling stage, I realized that I’d lost a special bolt and washer that attaches the brake cable to the brake. I dug around through my box of orphan bike parts and scrounged a bolt and washer designed for a completely different purpose that worked perfectly.
Next up: The Wild World of Dandelion Genetics