Glochid

a small barbed bristle occurring in the areoles of cacti :: Cactus glochids easily detach from the plant and become lodged in the skin, causing irritation upon contact. The tufts of glochids may cover some cactus species, each tuft containing hundreds of glochids; this may be in addition to, or instead of, the larger, more typical cactus spines, which do not detach.