Cacti are perennial thorny plants that emerged as a distinct family over 30 million years ago. Initially, they grew in South America, but later, with the help of humans, they spread to all continents. Some types of cacti grow in the wild in Russia.
What is a cactus?
All representatives of cactus have a peculiar structure that contributes to the accumulation of water. Their historical habitats are areas with low rainfall and hot climate. The whole body of the cactus is covered with hard, stiff thorns, which is a reliable protection from eating. However, not all cacti are prickly. The family also includes plants with ordinary leaves, and even small deciduous trees.
Since ancient times, the cactus has been widely used by humans. Several centuries ago, people who inhabited the growing areas of this plant used it in religious rituals, in medicine, and construction. Nowadays, cacti are even used as food! Plants from the opuntia group are traditionally eaten in Mexico, and both the stem and the fruit are used.
Due to its extravagant appearance, the cactus began to be used as an ornamental plant. Reliable hedges are created from large species. Small species have become widespread in pots and flower beds. Considering that the cactus does not require a lot of water, it has become very convenient for keeping in institutions and organizations, where watering of flowers is often very rare.
There are a huge number of cactus species in the world. The modern classification divides them into four large groups.
Pereskievye
These are exactly the plants that are officially considered cacti, but are not at all similar to them. The group includes only one type of shrub with normal leaves and no thorns. Experts believe that the peresian bush is an “intermediate” in the evolutionary chain of transformation of a deciduous plant into a classic cactus.
Opuntia
Plants from this group are distinguished by the most sharp spines of a complex shape. Each spine, called a glochidia, is jagged and very rigid in structure. Prickly pears rarely become food for animals or birds, since acute glochidia cause severe irritation of the gastrointestinal tract.
Another feature of this group of cacti is the segmental structure of the stems. They are made up of separate parts that are attached to each other. This is especially noticeable on young shoots.
Mauhyeny
The group is represented by only one species, which is distributed in South America. The historical place of growth is the Patagonia region. Cacti of the Mauhyenia group do not have sharp thorns, and the length of their leaves does not exceed one centimeter. Small seedlings, just emerging from the ground, strongly resemble ordinary deciduous plants. Therefore, it is difficult to determine the future cactus by their appearance.
Cactus
All other cactus plants are included in this group. The number of species is large, but they all have similar characteristics. For example, cactaceae lack any leaves. Their seedlings are difficult to confuse with deciduous plants, since they immediately have a spherical shape.
Representatives of this group do not have the sharpest spines-glochidia. Instead of them, the usual stiff thorns are located on the stem. The variety of forms of adult plants is great. This includes cacti with a vertical “trunk”, with a flat stem, creeping, forming columns. Some types of cactus intertwine, creating almost impenetrable thickets.
