Materials of plant origin are found in a wide variety of industries, including paper, food, textile, and construction—a list too long to mention here. But familiar examples are available in abundance: Chocolate is made from cocoa seeds, specifically seeds of the species Theobroma cacao. Foxglove (Digitalis purpurea) contains cardiac glycosides used to treat congestive heart failure. The berries obtained from the plant Piper nigrum produce black pepper; the berries are dried, resulting in black peppercorns, which can then be cracked or ground. Tea can be made from the leaves of Camellia sinensis. Fibers taken from the stem of flax plants (Linum usitatissimum) have been used to make linen, while the seeds are commonly consumed and are a source of linseed oil. Paper money is even made from flax fibers! The cardiac glycosides digitoxin contained in purple foxglove can be lethal if eaten, but in carefully administered doses it is used to treat congestive heart failure.