FRANGULA

A small, thornless tree, with broadly elliptical, smooth leaves. The bark occurs as thin, quilled pieces, greenish black externally with numerous elongated white linticels. 

It is medicinally used as a stimulant laxative, often incorporated in preparations with a bulk laxative such as Stericula or Ispaghula. The Frangula Bark is usually dried and seasoned for at least 2 years before use. 

Found in Potter's Cleansing Herb Tablets