The Second Cloud

I wrote spores leave beside forty microseconds. Then I went back to the frame. End-cup spores leave.

I was looking through the high-speed footage from a study of the Peruvian maidenhair fern. The researchers held a spore capsule by its stalk with tweezers. In one clip they recorded a hundred thousand frames per second and enlarged a strip originally just thirty-two pixels high. I laid some of those frames out in order beside the numbered stills in the paper. I could return to the same instant as often as I wanted. The dark shape beneath the tweezers was easier to follow than the flecks just beginning to leave it. Poppinga and colleagues’ recording and Figure 7.

I had come to the footage from a study of another fern. A band of cells called the annulus bends back as it dries, drawing the capsule open. Bubbles form in the water under tension inside the cells and the band recoils. The recoil slows sharply partway through. In Llorens and colleagues’ account, the slow movement of water through the porous cell walls helps explain that braking. I had been looking for the swing and the moment it slowed. Llorens and colleagues’ study.

In the maidenhair frames, the split capsule has two cups. The one at the moving end flings its spores first. In the next few frames the capsule bounces, and spores from the cup near the stalk shake loose. The researchers distinguish those departures even though both fit inside the same small burst of motion. I had made them share a verb in my first note. The study’s account of the release.

I opened a second clip and laid out its frames too. In the still marked two hundred microseconds, the first cloud stretches down the image in a loose trail. The second is higher and spreads sideways. For this pass I kept my attention near the stalk. There was a little jolt there, in the part of the picture I had been using as a fixed point. The second recording.