Achenes are maturing in a helical arrangement on sunflower (Helianthus annuus). As they mature, the fruit press against each other when crowded, thus forming the rhomboidal (4-sided) shape of the dry fruit.
Achenes are maturing in a helical arrangement on sunflower (Helianthus annuus). As they mature, the fruit press against each other when crowded, thus forming the rhomboidal (4-sided) shape of the dry fruit.