Hairy scales

Hairy scales [ Botany ] (Astrophytum anatomy)	Dictionary of botanic terminology - index of names
Synonyms: Woolly flecks, White dots, Woolly scales

Characteristic star like hair or scales covering the epidermis of the genus Astrophytum.

The epidermis of plants of the genus Astrophytum is more or less covered by white dots or flecks variously arranged sometimes along lines, sometimes according to more irregular patterns, this dots are a exclusive characteristic of this genus. The small white flecks vary and are lacking in some. Without the flecks the form is called 'nudum' .
The white dot are composed of very fine interwoven mostly radiating hairs, which, under a microscope, are very pretty objects.

Left: the woolly flecks of A. capricorne

FUNCTION OF THE WHITE DOTS:

The main utility of this scale seems to be the camouflage of the plant in their environment (stone-mimicry), also they protect the epidermis against the solar radiation cutting down the UV dosage.
They also proved to absorb water into the plant-body.

(stone-mimicry) A. coahuilense camouflaged among white stones

JAPANESE CULTIVARS.

The Japanese have a predilection for collecting weird mutants of genus Astrophytum. The more white and big flecks the better.

Two big flecked and very famous Japanese cultivars are Astrophytum asterias cv. SUPERKABUTO and Astrophytum myriostigma cv. ONZUKA. This plants are available in an outstanding wide range of unusual patterns. The dots themselves vary greatly in form and can be raised or very fluffy,
Usually roundish, but can be elongated, dendritic, V shaped, fly shaped etc..

Left: The typical hairy scales of cv. SUPERKABUTO

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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