Pod

Impatiens capensis, orange jewelweed, carries a second common name that gives away its trick: touch-me-not. Not the same touch-me-not as the one on /touch — Mimosa pudica gets called that too, for folding away from a finger. Jewelweed earns the name for the opposite reason. Its ripe seed pods sit under real mechanical tension, and the lightest touch at the tip is enough to set them off: four valves split and coil backward in a few thousandths of a second, and the seeds inside don't fall, they launch.

Hayashi, Feilich & Ellerby (Journal of Experimental Botany, 2009) filmed it to find out how. The valves are a two-layer structure held under turgor pressure — live water pressure, not a dead spring — and when the pod's own tension finally exceeds what's holding it shut, splitting and coiling both finish in 4.2±0.4 ms. That's faster than a human blink, and fast enough that the valve tissue itself, weighed right after a burst, is still about 85% water: nothing dried out to cause this, the trigger is entirely mechanical. Touch the pod below.

What launches isn't aimed by anything. The valves coil the same way every time regardless of where a seed happens to sit against them, so the room draws each seed's own launch speed and angle from the actual ranges the 2009 study measured across real bursts: speed anywhere from 0.2 to 4.08 m/s (a touch, not a threshold — the fastest seed and the slowest are the same explosion), and an angle averaging 17.4° above horizontal, close to the angle a ballistic model predicts would carry a seed of this size and mass farthest — not straight out, and not straight up, but the shallow middle a real trebuchet operator would also pick. A ripe pod carries 2 to 5 seeds, averaging 3.46, so each touch launches a small, real handful, not one.

Honest gap: the study's 17.4° is a mean of 45 measured seeds with a reported error of ±5.2° on that mean — a statement about how precisely the average is known, not about how much any one seed's own angle varies from the next. This room still needs some spread to look like a real spray rather than 45 identical copies, so it adds its own ±12° scatter around 17.4° as a disclosed illustrative liberty, not a measured figure. The room also only ever launches to the right; a real burst sends seeds in every direction around the pod's own axis, not one half of a circle. And a fresh pod appears a couple of seconds after each burst so this stays repeatable in a browser tab — real regrowth takes a season, not a couple of seconds, the same clock-compression /touch and /cone already take with their own plants' real timing.

Sources: Hayashi, Feilich & Ellerby, The Mechanics of Explosive Seed Dispersal in Orange Jewelweed (Impatiens capensis), Journal of Experimental Botany 60(7), 2045–2053 (2009).