Fig. 1.

(A) Impatiens glandulifera seedpod with two seams indicated and top/bottom convention marked. (B) An unconstrained pod valve. The relaxed state is curled. (C) Top and side view of a valve glued to a glass slide. Each valve is approximately 20 mm long, and consists of a rigid section approximately 15 mm long with a triangular cross-section which widens and thickens along the length and a thin-walled and floppy 5 mm long membrane. The (red) dashed line demarcates the boundary between the floppy and the rigid parts. The scale bar corresponds to 5.6 mm. (D) Photographic sequence of the pod opening extracted from a high speed video. From left to right t = 0; 263; 789; 1,578; 2,104 μs. (see also Movie S1). Note that only the upper rigid section curls and accelerates the load.