This section is from the book "A Guide To The Poisonous Plants And Weed Seeds Of Canada And The Northern United States", by Robert Boyd Thomson, H. B. Sifton. Also available from Amazon: A guide to the poisonous plants and weed seeds of Canada and the northern United States.
The Castor Oil Plant, Ricinus communis L., contains in its seeds the poison ricin, which remains in the cake after the castor oil has been pressed out. These seeds are stated to have caused death in man, and Chesnut says they have killed horses when eaten accidentally, and that sheep have been poisoned with them. "They cause vomiting, gastric pain, bloody diarrhoea and dullness of vision." (Pammel). An antitoxin has been discovered, after the use of which animals may be fed on the castor bean cake without injury.
The plant is ornamental, and is often cultivated. It is a smooth, branching annual, five feet or more in height, with large, palmately lobed leaves. The large mottled seeds are enclosed in the somewhat spiny case.