Iodine is a chemical element with symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a lustrous, purple-black metallic solid at a standard conditions that sublimes readily to form a violet gas. The elemental form was discovered by the French chemist Bernard Courtois in 1811.
Definition of CHOLLA. : any of numerous shrubby opuntias chiefly of the southwestern United States and Mexico that have needlelike spines partly enclosed in a papery sheath and cylindrical joints âcalled also cholla cactus.
A cactus (plural, cacti) is a type of succulent plant belonging to the dicotyledonous flowering plant family, Cactaceae. The Cactaceae has around 90 genera and some 1,500 to 1,800 species.Cacti are well-known natives of the Americas, mostly found in desert areas.he leaves have evolved into spines, which in addition to allowing less water to evaporate than regular leaves, defend the cactus against water-seeking animals. Photosynthesis is carried out by enlarged stems, which also store water.