The petals may be united to form a tubular corolla (gamopetalous or sympetalous). Flowers are sympetalous, most often divided into five lobes (petals). A sympetalous flower, with bilateral symmetry with an upper and lower lip, is bilabiate. The sympetalous, insect-pollinated flowers are five-parted and either yellow or white. The corolla is sympetalous, with five petals, often bilabiate.