The first soaps were probably the saps of certain plants, such as the Soap Plant (Chlorogalum pomeridianum), whose roots can be crushed in water to form a lather, and used as a shampoo. Other plants, such as Soapbark (Quillaja saponaria), Soapberry (Sapindus mukorossi), and Soapwort (Saponaria officinalis) also contain the same main ingredient, a compound called saponin, which forms the foamy lather, and is also a toxin used to stupefy fish in streams to make them easy to catch. Later, people learned that fats would react with alkalis in the ashes left over from a fire to produce saponified compounds such as sodium stearate and the related potassium stearate. Today, soaps are made from fats and oils that react with lye (sodium hydroxide). Solid fats like coconut oil, palm oil, etc., are used to form bars of soap that stay hard and resist dissolving in the water left in the soap dish. Oils such as olive oil, soybean oil, or canola oil make softer soaps.