True cinnamon comes from a Sri Lankan tree of the species Cinnamomum verum (also called Cinnamomum zeylanicum) or, more precisely, from its oil-rich bark, which is hand harvested, scraped clean of its woody outer layer, and dried in delicate, multilayered quills (see A Pure Food); whole or ground, it has a mellow flavor, warm and sweet all at once. Cassia comes from several species of tree also belonging to the Cinnamomum genus, with significant harvests in Indonesia, Vietnam, China, and the Indian Subcontinent (see A Cinnamon Glossary). Its bark is thicker than cinnamon's, making for stiffer, sturdier quills. Cassia is sharper in taste, with a pronounced heat. It can also have a bitter edge and for that reason is often knocked as inferior to cinnamon. In truth, each spice offers its own advantages.