Definition of "gadroon"

Owing possibly to some flaw in his mental make-up, Uncle Tom has been collecting old silver since I was so high […] . I knew all about that collection of his, not only because I had had to listen to him for hours on the subject of sconces, foliation, ribbon wreaths in high relief and gadroon borders, but because I had what you might call a personal interest in it, once having stolen an eighteenth-century cow-creamer for him.

1960, P. G. Wodehouse, Jeeves in the Offing, chapter V