"Flower-cluster of yarrow (Achillea Millefolium). A, head seen from above; B, longitudinal section; re, receptacle; ch, chaff; i, involucre; r, ray-flowers; d, disk-flowers; c, corolla; s, stigma." -Bergen, 1896

Yarrow

"Flower-cluster of yarrow (Achillea Millefolium). A, head seen from above; B, longitudinal section;…