They are tulips. According to the book "The Fraktur-Writings or Illuminated Manuscripts of the Pennsylvania Germans" by Donald A. Shelley...
"The Tulip was the most favored of all flower motifs, whether on pottery, glass, china, pinted tin, butter molds, furniture, or on Fraktur".
They were common on engraved powder horns. Several rifles are pictured in "Rifles of Colonial America" with tulip carving.
It didn't develop in America... it came here from Europe. According to Shelley... "the tulip was first seen at Vienna about 1559".