Abnormal

Abnormal [ Botany - Biology ]	Dictionary of botanic terminology - index of names
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A term generally used to refer to characteristics that are unconforming to those of the norm.

Any change from the average, not necessarily harmful. Not normal; not typical or usual or regular .
Different from the most common pattern found in a particular species, organ or tissue in e.g. shape, colour, size, functionality or development.
However, the word "normal" has no clear boundaries, therefore the word "abnormal" can only ever be relative to that of normal.

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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