The Cactus family is one of the many groups of the order succulents. Cacti and Succulents differ from many other species because of their ability to survive drought and other harsh climates and conditions. For example, many succulents have adapted to the arid climates of deserts and semi-deserts. Many succulents evolved in the cold, apline regions of Europe, where they adapted to the poor, rocky soil and strong winds. Other succulents evolved in the jungles of central and South America, and also evolved on the beaches where the salt concentration was extremely high. Succulents have the ability to store noursihing ingredients in their stems, roots and leaves. That is why the word "succulent" in latin is "succos" meaning juice.
Spines and Thorns
Nearly all cacti and some succulents have spines, which are actually modified leaves. Cactus spines grow out from areoles, but succulent spines grow directly from the skin tissue. Cactus and Succulent spines vary in shape, sixe and texture. Some are short and bristly; others are softly curved, but visously barbed. They also range in color from white, red or yellow to black. Although spines provide defense against predators, their main function is to condense moisture in the air so that it drips onto the ground, providing the plant with vital water. Spines can also be wolly and hairlike. This hair or cephalium shields the plant from cold and fierce sun. Some succulents have throns which are modified flowers, leaf stalks or leave buds.
Pseudocephalium, A mass of woolly spines that grows on one
side of the stem. Only Melocactus and Discocactus have a
true cephalium on the crown.
Cacti and succulents have developed many different surfaces and textures depending on their environmental climate of their habitat. For example some plants that thrive in high altitudes with fog have felted or hairy surfaces that enables then to trap in moisture. In regions where the temperature is hotter, lightly-colored folage reduces heat absorbtion. They also may have a waxy coating known as cutin. Succulent leaves and cactus stems have few stomatas, or suface pores to minimize water loss. In cacti and many succulents these pores are closed during the day and open in the night (when the temperature decreases) the stomatas open to absorb carbon dioxide, which is used the next day for photosynthesis.
Regions where it is very arid and where long dry spells enforce cacti and succulents to remain in a dormant state for most of the year. Cacti and succulents have developed a very short growing season. As soon as the rain falls, cacti and succulents burst into a growth, forming leaves, flowers and seeds in less than a month. Cacti flowers have evolved in several different ways to attract pollinators. Most desert cacti flower in daytime, producing an uncented, but magnificently colored flower to attract flying insects. Many jungle cacti bloom at dusk. These blooms are large, pale and richly perfumed so pollinating moths can locate the flower. Also, some night-flowering cacti produce foul cented, fleshy flowers to attract bats. Even some cactus blooms have a tubular flower to accommodate the beak of a humingbird.
Fruits and Seeds
A succulent flower must be pollinated to produce seeds and fruits. By to doing so, the pollen from the flower's anther must be transferred to the stamen of another plant in that genus. Once the pollination is successful, the flower withers and the ovary developes into a fruit containing seeds. Cacti and succulents have fleshly fruits or berries. The seeds from the fruit are dispersed by water, wind, insects, birds or rodents. Mesembryanthemum seeds are sealed in woody pods, and open in when dampend by rain. If the pods dry out, they close until more rain arrives.
Discovery and Distribution
Originally cacti grew only in the American continents. Succulents were native to many regions from northern Europe to the Far East, however, most were concentrated in southern and eastern Africa. Major expeditions began in the late 15th century during the race to find a western sea route to India. During many expeditions, new species of plants were found. Christopher Columbus is known to be one of the first people to have taken the first cactus to Europe, and presented these "weird" (as it appear then), leafless plants to Queen Isabella of Spain. Meanwhile many explorers such as Vasco de Gama discovered succulents in southwestern Africa and India.
As the intrest in succulents rose, more and more botanical expeditions were performed. In 1777-1787, King Charles III of Spain sponsored several major expeditions to the Americas. Many more expeditions were held and cacti and succulents are still constantly being introduced to cultivation.