Defasciation

Defasciation [ Botany ]	Dictionary of botanic terminology - index of names
Synonym: To break in individual apexes

The origin of normal shoots from crest meristems.

(Photo 4) Mammillaria luethyi forma cristata a line crest completely defasciated	The defasciation is a process leading to longitudinal cleavage of a linear crest, rather to the complete division of the stem into individual normal shoots. Crests may remain at any stage for a long time. But at the stage of brain-shaped crest when the curves begin to crowd defasciation occurs rather often. That is the linear meristem turns into a number of small apical meristems that form normal shoots. More seldom defasciation occurs without any reason at an earlier stage of the development of the crest.
		Mammillaria theresae forma polytomica (Derived from crest defasciation)
In general with age meristem gets less active or not active at all. The growth continues only at some parts of linear meristem. Thanks to this process the upper surface becomes uneven. The more active parts are usually situated at its ends. This type of developing crest prevails among cacti, and for a long time it was considered to be the only possible.

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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