Which plant's seeds are used to produce the poison abrin, which is similar to ricin?

The seeds of Abrus precatorius are used to produce abrin, and the plant is commonly called the jequirity bean or rosary pea. Abrin is a highly toxic protein that disrupts ribosomes, preventing cells from making essential proteins.

The seeds are strikingly colored, usually red with a black spot, which explains their historical use as beads, jewelry, and percussion-instrument components. Their hard outer coat can protect the toxin if a seed is swallowed intact, but chewing, cracking, or piercing the seed can release abrin and make it extremely dangerous.

A common mix-up is castor bean, whose seeds contain ricin rather than abrin. Both toxins are ribosome-inactivating proteins, which is why they are often compared, but they come from different plants. The seeds have also served as a traditional unit of weight in South Asia, known as the ratti, because individual seeds are remarkably uniform in mass.