Melocactus

The genus Melocactus includes about 30 different types of cactus. Native to the Caribbean, the West Indies, the Bahamas and northern Latin America, they are among the most endangered species in the world. 

They are recognizable by their cephalium, a woolly structure that develops on the top of the plant. Growing Melocactus is a delicate process, as they are very slow to grow and are sensitive to humidity and to rotting.