Raphides

Raphides are crystalline inclusions found in the cytoplasm of certain plant cells, particularly in the endosperm of seeds. They are composed of calcium oxalate and are often referred to as "sand grains" due to their small, sharp, and angular shape. Raphides serve multiple functions in plants, including mechanical support, protection, and defense against herbivores. Their sharp edges can cause injury to the mouth and digestive tract of animals that consume the seeds, thereby acting as a deterrent. Additionally, raphides can contribute to the structural integrity of the cell, providing rigidity and strength. They are commonly observed in the seeds of plants such as castor beans, flax, and certain grasses. The presence of raphides can vary among different species and even within the same species, depending on environmental and genetic factors.