Capsicum
Most of the capsaicin in a pepper is found in the interior ribs that divide the chambers of the fruit, and to which the seeds are attached. At the stem end of the pod, glands secrete the capsaicin, which then spreads throughout, but is concentrated on the ribs and seeds. The amount varies very significantly by variety, and is measured in Scoville heat units (SHU), ranging from the mild bell pepper to the scorching Habanero chile.