in botany, a genus of the syngenesia polygamia frustanea clas. The receptacle is bristly; the pappus is simple; the rays of the corolla are tunnel-shaped, long, and irregular. There are 61 species, five of which are natives of Britain, viz., the cyanus, or blue-bottle; the scabiosa, or great knapweed; the jacea, or common knapweed; the calcitrapa, or star-thistle; and the solstitialis, or St Barnaby's thistle.