Living rock cacti

Living rock (plants) [ Horticulture ]	Dictionary of botanic terminology - index of names
Synonyms: Mimicry Stones (plants), Living stones (plants).

The term “living rock ” refers to several genera of dwarf, cryptophyte succulent plants that live almost buried in the ground and resemble (for colour and texture) the surrounding soil surface and stones among they grow .

A. fissuratus
Photo and © Copyright by Marco Antonio Arroyo - Mexico )
The mimetic colouring of a plant in its natural habitat in Cuatro Cienegas, Coahuila - Commonly called "living rocks," these cacti usually blend in well with the terrain around them.
Lithops hookeri subfenestrata C19
A "living rock" that comes from the equally shiny dark and implausibly shiny ironstone substrate.

Living rock cacti: The term “living rock cactus” refers to several Mexican genera of dwarf, cryptophyte cacti plants, and particularly to cacti belonging to the genus Ariocarpus (especially A. fissuratus).
The “living rock” are low-growing plants that live almost buried in the ground and often have a rosette of tubercles that are flattened and resemble (for colour and texture) the surrounding soil surface. Most of this plants almost entirely lack spines but are covered by warty tubercles and woolly hairs, so they often mimicry the stones among they grow (hence the name living stones). Water is stored against the dry season in the thickened tap-root or in the underground plant body reservoirs. Often these plants melt so efficaciously with the background that are completely invisible if not flowered.
Other cacti that are usually called living rock comprises:
Astrophytum, Aztekium, Epithelantha, Geohintonia, Lophophora, Obregonia, Turbinicarpus and Strombocactus
Living rock mesebrianthemums: The term living rock (or living stone) is also used to indicate several South African members of the Aizoaceae family (especially Lithops) that are highly succulent stemless clump-forming plants with variously coloured leaves similar in texture to lumps of rock. The colour of the plant is that of the natural rock where they live. Other succulent that are usually called living rock comprises: Pleiospilos, Conophytum, Titanopsis, Lapidaria, ecc..

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Holdfast roots [ Botany ]
Dictionary of botanic terminology - index of names

Some species of climbing plants develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place.

Climbing plants, like the poison ivy (Toxicodendron radicans), Boston ivy (Parthenocissus tricuspidata), and trumpet creeper (Campsis radicans), develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place. Usually the Holdfast roots die at the end of the first season, but in some species they are perennial. In the tropics some of the large climbing plants have hold-fast roots by which they attach themselves, and long, cord-like roots that extend downward through the air and may lengthen and branch for several years until they strike the soil and become absorbent roots.

Major references and further lectures:
1) E. N. Transeau “General Botany” Discovery Publishing House, 1994