Cacti have either a long tap root or fibrous roots just below the surface of the ground.
Yes, cacti are dicots. Dicots are a type of flowering plant that have two seed leaves, whereas monocots have one seed leaf. Cacti belong to the class Magnoliopsida, which includes dicots.
It's spelled cacti. The plural form of cactus is like the plurals for octopus and pegasus (e.g. octopi and pegasi). These particular words are spelled in exactly the same way as their Latin root words would be, so the us is changed to i.
Cacti, succulents, and wildflowers are examples of flowering plants that can be found in desert ecosystems. These plants have adapted to thrive in arid conditions by storing water and having specialized root systems.
One cactus, two cacti
Some cacti have a tap root while others have a dense fibrous root system.
tap root
I water my Mammillaria cacti once the soil has dried out completely. This is recommended for all cacti, it is better to water them not as often rather than regularly because if you get root rot then your cacti will die.
Stop Watering it, let the soil dry out between waterings
cactus for a single plant cacti for plural
Cacti utilize a type of photosynthesis called CAM (Crassulacean Acid Metabolism) to survive in arid environments.
You could suppose that cacti of the same type look similar. They will have the same color patterns and spines, but will most likely be shaped differently.