All parts of the rhubarb plant contain oxalates, which are poisonous in sufficient quantity. Rhubarb also contains anthraquinone glycosides, which probably contribute to its toxicity.

The first head protection concept introduced to the biking world was a hat made from pith, which is the spongy rind found in the stem of sola plants, aeschynomene aspera. Pith helmet craftsmen ...

Huffman and others have also seen chimps chewing the bitter pith of a plant called Vernonia amygdalina to treat worm infections. But that behavior is not unique to primates.