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   Why ferns are hard to identify
   Illustrated Glossary
   Flora of Australia
   Lower Vascular Plant Glossary
Hardy Fern Glossary
   Structure and Shape
   Blade Division
   Hairs and Scales
   Sori and Indusia
Major Fern Links

    Adiantum  Arachniodes
    Aspidotis  Asplenium
    Astrolepis  Athyrium
    Blechnum  Cheilanthes
    Cryptogramma  Cyrtomium
    Cystopteris  Dennstaedtia
    Deparia  Diplazium
    Dryopteris  Gymnocarpium
    Lygodium  Matteuccia
    Onoclea  Oreopteris
    Osmunda  Pellaea
    Phegopteris  Pleopeltis
    Polypodium  Polystichum
    Pteridium  Pteris
    Pyrrosia  Thelypteris
    Woodsia  Woodwardia

Glossary: Hairs and Scales

Hairs, glands and scales together constitute the surface ornamentation or indument of a structure (rhizome, stipe, rachis, costa, lamina, indusium). With a lack of all of these the structure is called glabrous. If the hair or scale falls off early in life, the surface or structure is called glabrescent and the hair or scale deciduous. The specific type of indument is characteristic, sometimes diagnostic, for genera or species.

What is the difference between a hair and a scale? One cell. Hairs are one cell in width or depth. Narrow scales sometimes cannot be differentiated from hairs with the naked eye, but you can usually do so with a hand lens.



A number of technical terms are used to describe needle-like hairs, among them
acicular hair ciliform hair setiform hair
Surfaces covered with hairs are described this way:
hirsute surface lanate surface pilose surface surface
sericeous surface strigose surface tomentose surface villous surface


This capitate hair with an enlarged tip is also a gland.
capitate hair/gland
When the gland is not at the tip of a hair, but sitting right on the surface, it is sessile.


Most scales are described by their shapes, for example, linear or ovate, but there are special types of scales too:

bullate scale clathrate scale denticulate scale fibrillose scale
(stained-glass effect)

Another scale type, peltate, a round scale attached near the center, is found in Polypodium polypodioides.

All the line drawings here are from A Modern Multilingual Glossary for Taxonomic Pteridology, David B. Lellinger, American Fern Society, 2002, with permission.
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