raphides

plural noun, singular ra·phide [rey-fahyd] /ˈreɪ faɪd/, ra·phis [rey-fis] /ˈreɪ fɪs/. Botany.

1. acicular crystals, usually composed of calcium oxalate, that occur in bundles in the cells of many plants.

Plural raphides (răf′ĭ-dēz′)

1. One of a bundle of needlelike crystals of calcium oxalate occurring in many plant cells. The crystals discourage animals from eating the plant by irritating their tissues.