Eupatorium perfoliatum

Possibly engraved by W. B. Annin or Annin and Smith from a drawing by Jacob Bigelow(?).Colored engraving of "Eupatorium perfoliatum" or Thoroughwort (Figure 1) with a "flower magnified" (Figure 2), "floret magnified" (Figure 3), and "tube of anthers with style running through" (Figure 4)