Figure 2.

Ballistospore launching upon drop coalescence. (a) Prior to the launching of a ballistospore, a spherical Buller's drop forms at the hilar appendix which is at the base of the spore, and a lens-shaped drop forms on the adaxial side. The spore is supported by a sterigma with an abscission zone indicated by the dotted area. (b–e) Conceptual model for ballistospore launching, where a spore-shaped particle is launched from a supporting substrate by the capillary–inertial process. The blue (dark) arrow denotes the force exerted on the merged drop by the particle, and the purple (light) arrow denotes the counter-force exerted on the particle. At the point of launching in (d), the net acceleration of the merged drop is zero and the compressive force between the particle and the substrate vanishes. Note that the sterigma is rotated 90° relative to figure 1.