The tares in the parable refer to the seed called "darnel," a rank and widely distributed grass, and the only species that has deleterious properties. It- is poisonous and its grains, if eaten, produce vomiting, purging, convulsions and sometimes even death. Before it comes into the ear it resembles the wheat so closely that it can hardly be distinguished from the latter, hence the command to leave it to the harvest. Grain-growers in Palestine believe the tares, or suwan, to be a diseased or degenerate wheat. The seed resembles wheat in form, but is smaller and nearly black.