Scion

Scion [ Horticulture ]	Dictionary of botanic terminology - index of names

The upper part of the union of a graft

A scion is an unrooted portion of stem used to propagate a new plant containing almost a bud, taken from the desired plant which is then grafted onto the rootstock of another plant. The scion is usually an aerial plant part, often a branchlet or a single bud, that is grafted onto the root-bearing part of another plant (the understock). The scion holds the flowering or fruiting characteristics of the plant which is joined by grafting; the root stock enables it to grow quickly. Hence a grafted plant consists of a scion (above ground growth) and a rootstock (below the ground growth).

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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