Once achenes ripen, they are ejected by staminodes, which remain under tension until that time. (Pollen is also explosively shot into the air; one tropical species, P. microphylla, is even called "cannon plant" for that.)
Ripe achenes are straw-colored and streaked with dark purple or brown. Achene color is an important diagnostic character enabling separation of this species from the less common P. fontana, which produces dark purple to completely black achenes.