An outline of the evolution of "living fossil" cactus

   has evolved more unique species in the history of horizontal development of cactus. The cactus with especially short lateral teeth evolved into a palm-shaped or multi-node-shaped species.

(as the cactus refers to the famous Christmas cactus), these species are easy to reproduce by cutting off or shedding nodes on their own.

   creeping cactus grows particularly fast because buds lying on the ground quickly take root.

The cactus    can be cut into several segments unscathed because each segment has a separate fibrous root. This method of propagation can also be used to cross the rootless stage of seedlings or stem nodes.

The succulent plant of    cactus can store a lot of water and belongs to succulent plant. Therefore, in addition to the dry early area, the cactus also occupies a broader living space. In wetter areas, there is no shortage of rather dry places, and plants that cannot store water (such as on rocks) are difficult to survive. So we often find cacti and other succulent plants on flat rocks.

   doesn't need to change much from being born on rocks to living in trees. Non-parasitic plants that live on other plants are called epiphytes. This way of life is obviously very beneficial to small plants, such as in dense forests, small plants attached to the canopy can get more light, but they cannot thrive in the dark ground. epiphytic life style requires plants to have the ability to absorb and store water quickly, because there is so little soil on the branches or in the cracks in the bark that the water will evaporate in a short period of time. Epiphytes usually have aerial roots to facilitate rapid absorption of Rain Water. Although epiphytes can store water well, they can only occur in large numbers in tropical areas with abundant precipitation.

   has only lower epiphytes such as lichens and moss in Germany. Although it dries up after every rain, it does not affect their survival. Higher epiphytes can't stand drought, so they are used to storing water. Unlike parasitic plants, epiphytes do not have to be attached to other plants, and many epiphytes occasionally grow on rocks. Artificially cultivated epiphytes also grow well in flowerpots, even more luxuriantly than epiphytes in tree skills. The reason is that trees usually grow faster than epiphytes, so even epiphytes growing in the crown often do not get enough sunlight. This leads to the gradual increase of the surface area of epiphytic cactus in the process of evolution to get more light. Their buds are either flat (such as leaf-shaped cacti or multi-jointed cacti) or only a few millimeters thick (such as Reed or Hatiola), and the dense spines originally used to protect themselves from animals have become sparse or bristled.

Although    leaves (which have been degraded and disappeared in the history of cactus development) are beneficial to the growth of daughter plants in this environment, cactus does not regenerate leaves, but produces flat buds instead of leaves. Because in the history of the development of cactus, it is impossible to appear the same genetic characteristics twice and reproduce them in the same way. Degenerated and vanished complex organs (such as leaves) cannot be regenerated and will at most be replaced by completely different new organs (such as flat buds), which is an important law in biology (Doro's law). Epiphytic cactus is also derived from the common cactus, which is more obvious in its seedling stage. Adult epiphytic cacti often have many ridges and hard spines or hard bristles. Cactus as a typical plant in arid zone

Its ability to absorb and store water is first-class, and it can make use of its own stored water for early needs. This ability makes them suitable for epiphytes because water supply is relatively difficult under such living conditions.

In addition to   , the reproduction of epiphytic cactus is also difficult. If you scatter the seeds like an ordinary cactus, the seeds will fall into the dark sky.

The forest ground of the sun and it is difficult to fall on the branches. Therefore, most epiphytic cacti have succulent berries that birds like to eat, and the seeds are dominant. When birds peck open the berries, the seeds will adhere to the skill. Most epiphytic cacti retain the early dwarf shrubby form, at least with woody features at the base. Most climbing cacti are the same as epiphytic cacti. Its slender buds can grow quickly to the high and bright places in the forest. The thin and thin cactus can easily cling to other plants or rocks with its thorns without falling off.

   winding cactus is even more capable of climbing and growing, because of its long buds and butterfly-shaped growth, people often call them serpentine cacti. This kind of cactus usually takes root in favor of climbing. In addition, aerial root also plays a more important role in obtaining water. Because climbing cacti often have slender stems several meters long, it is difficult to supply water from the roots to the top. When such cacti completely abandon their underground roots, they also evolve into epiphytic cacti, such as epiphyllum. This kind of "crawling" cactus should be the cactus with the longest stem. For example, the Mexican ruler can grow to a hundred meters long. The county flower genus and its related genera clearly reflect the genetic relationship with epiphytic and climbing cactus.

. They are very similar to the climbing serpentine cactus, and even hybrids between the two genera have appeared.

In the evolutionary history of    cactus, the morphology of most cactus is similar to the original species of shrub type. New varieties are usually bred from earlier original species, and the shape of the seedling stage is often maintained until adulthood. This phenomenon is quite common in the evolutionary history of animals and plants. For example, herbaceous plants are generally interpreted as descendants of woody plants. As far as the evolution of cactus is concerned, the general rule is that the characteristics of Lignification and differentiation gradually weaken in the process of evolution.