Caudiciform plants, or fat plants, are water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

-retaining plant

Plant

Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s adapted to arid

Arid

A region is said to be arid when it is characterized by a severe lack of available water, to the extent of hindering or even preventing the growth and development of plant and animal life...

 climate or soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

 conditions. Caudiciform plants store water in their stem

Plant stem

A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...

 bases, stems

Plant stem

A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...

 and/or root

Root

In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...

s. Many species of plant from different plant families have developed this form of storing water rather than in foliage or in fat leafless stems. Consequently, many caudiciform plants have temporary shoots and leaves that die back to the caudex

Caudex

A caudex is a form of stem morphology appearing as a thickened, short, perennial stem that is either underground or near ground level . It may be swollen for the purpose of water storage, especially in xerophytes...

 or tuber at or underground when conditions become too dry and regrow once conditions improve.

Many caudiciform succulents come from the dry areas of the tropics

Tropics

The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately  N and the Tropic of Capricorn in the southern hemisphere at  S; these latitudes correspond to the axial tilt of the Earth...

 and subtropics

Subtropics

The subtropics are the geographical and climatical zone of the Earth immediately north and south of the tropical zone, which is bounded by the Tropic of Cancer and the Tropic of Capricorn, at latitudes 23.5°N and 23.5°S...

, such as steppes, semi-desert and desert

Desert

A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...

. High temperatures and low precipitation

Precipitation (meteorology)

In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...

 force plants to collect and store water in order to survive long dry periods.

Families and genera that include caudiciform plants are:

• Aizoaceae
  Aizoaceae
  The Family Aizoaceae or Ficoidaceae is a taxon of dicotyledonous flowering plants containing 135 genera and about 1900 species. They are commonly known as stone plants or carpet weeds. Species that resemble stones or pebbles are sometimes called mesembs...
  
  : Sphalmanthus
• Apocynaceae
  Apocynaceae
  The Apocynaceae or dogbane family is a family of flowering plants that includes trees, shrubs, herbs, and lianas.Many species are tall trees found in tropical rainforests, and most are from the tropics and subtropics, but some grow in tropical dry, xeric environments. There are also perennial herbs...
  
  : Adenium
  Adenium
  Adenium is a genus of flowering plants in the dogbane family, Apocynaceae.-Cultivation and uses:Adenium obesum is grown as a houseplant in temperate regions. Numerous hybrids have been developed. Adeniums are appreciated for their colorful flowers, but also for their unusual, thick caudexes...
  
  
• Passifloraceae
  Passifloraceae
  Passifloraceae is a family of flowering plants, containing about 530 species classified in around 18 genera. They include trees, shrubs, lianas and climbing plants, and are mostly found in tropical regions....
  
  : Adenia
• Asteracea: Othonna
  Othonna
  Othonna is a genus of evergreen or deciduous geophytes, dwarf succulents or shrubs belonging to the sunflower family Asteraceae. The genus includes more than 100 species concentrated in the Western Cape of South Africa and southern Namibia. A few species occur in summer rainfall parts of southern...
  
  
• Curcubitaceae: Kedrostis
• Euphorbiaceae
  Euphorbiaceae
  Euphorbiaceae, the Spurge family are a large family of flowering plants with 300 genera and around 7,500 species. Most are herbs, but some, especially in the tropics, are also shrubs or trees. Some are succulent and resemble cacti....
  
  : Euphorbia
• Orchidaceae
  Orchidaceae
  The Orchidaceae, commonly referred to as the orchid family, is a morphologically diverse and widespread family of monocots in the order Asparagales. Along with the Asteraceae, it is one of the two largest families of flowering plants, with between 21,950 and 26,049 currently accepted species,...
  
  : Oeceoclades
  Oeceoclades
  Oeceoclades is a genus of flowering plants from the orchid family, Orchidaceae.- References :*Pridgeon, A.M., Cribb, P.J., Chase, M.A. & Rasmussen, F. eds. . Genera Orchidacearum 1. Oxford Univ. Press....