• Crystals are an important protective feature in some plants' genetic makeups. Just as a porcupine has quills for protection or an octopus releases a black fog as defense against an enemy, some types of plants have crystals that keep herbivores away. While some plant species are dangerous to eat because they contain poisons, other plants contain crystals within them. For some plants, crystals serve as a natural defense system that makes eating the plant less appetizing.
  
  

Druses

• One type of plant crystal that can be found on some household species is called a druse. The druse has a round or spherical shape and is small enough that it can not be seen with the naked eye. The druse, which can be found on the foliage and stems of plants, has a gritty texture. According to Dr. Gary Coté in Science Codex, druses in a plant can scratch the inside of an herbivore's mouth as it attempts to eat the plant. Dr. Coté parallels this eating sensation to that of chewing sand. Even though it is not poisonous to the animal ingesting the plant, the gritty texture can be quite unappealing.
  
  

Raphides

• A raphide is a crystal that works to protect the plant from being eaten. Raphides are longer than druses and are slender in shape. They are most often found in small cluster-like groups. According to e! Science News, these needle-like crystals are most frequently found in the leaves of a plant. Due to their convenient access for most animal species, leaves are the most common portion of a plant to be eaten. The act of chewing the leaves is what typically separates and expels the raphides from the leaves. However, Dr. Coté explains that these crystals turn into what could be called microscopic darts upon consumption.
  
  

Prisms

• Some plants contain prisms. Prism-like crystals are only found in a mixture with pollen. As a result, according to Dr. Coté, prism crystals for plants may play a role in germination or the spread of pollen from one plant to another.
  
  

Crystal Makeup

• Regardless of the type of crystal found throughout the plant, be it druse, raphide or prism, all crystals contain calcium oxalate, which is the same chemical substance that comprises kidney stones in humans.