The glue applied on envelopes is of two types. There is the glue applied to the flap which is stuck by the consumer and is usually a gum. A distinctive natural gum is gum arabic, which comes from a substance fabricated by the acacia tree. The other glue which holds the rest of the envelope is stronger and more permanent. This glue is regularly derived from starches that are acquired from corn, rice, wheat, potatoes and other plants.