Mixed Cactus Seeds
Cacti are distinctive and unusual plants which have adapted to extreme arid environments, showing a wide range of anatomical and physiological features which conserve water. Their stems have expanded into green succulent structures containing the clorophyll necessary for life and growth, while the leaves have become the spines for which cacti are so well known.
Cacti are believed to have evolved in the last 30 to 40 million years. Long ago, the Americas were joined to the other continents, but separated due to continental drift. Unique species in the New World must have developed after the continents had moved apart. Significant distance between the continents was only achieved in around the last 50 million years. This may explain why cacti are so rare in Africa; the continents had already separated when cacti evolved. Many succulent plants in both the Old and New World bear a striking resemblance to cacti, and are often called "cactus" in common usage. This is, however, due to parallel evolution; none of these are closely related to the Cactaceae.
Cacti come in a wide range of shapes and sizes. Some grow to great size. Cactus flowers are large, and like the spines and branches arise from areeoles. Many cactus species are night-blooming, as they are pollinated by nocturnal insects or small animals, principally moths and bats. Cacti range from small and round to pole-like and tall, such as the Saguaro.