"Head of yarrow. A, top view; B, lengthwise section. re, receptacle; i, involucre; r, ray-flowers; d,…
"Flower-cluster of yarrow (Achillea Millefolium). A, head seen from above; B, longitudinal section;…
Achillea millefolium variation rubrum has red flowers. It is a variety of yarrow or milfoil.