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LICHENS AS DYE-PLANTS 417
boiling. Teloschistes flavicans and Letharia vulpina yield very similar yellow
dyes, and from Lecanom parella (Fig. 39), Pertusaria melaleuca and Usnea
barbata yellow colours have been obtained. Candelariella vitellina and
Xanthoria lychnea both contain yellow colouring agents and have been
employed by the Swedes for dyeing the candles used in religious ceremonies.
g. COLLECTING OF DYE-LICHENS. Lauder Lindsay 1 made exhaustive
studies of dye-lichens both in the field and in the laboratory, and recorded
results he obtained from the micro-chemical examination of 540 different
specimens. He sought to revive and encourage the use of their beautiful
colour products among country people; he has given the following practical
hints to collectors:
1. That crustaceous dwarf pale-coloured species growing on rocks, and
especially on sea-coasts, are most likely to yield red and purple dyes similar
to orchil, cudbear or litmus; while on the other hand the largest, most handsome
foliaceous or fruticose species are least likely.
2. That the colour of the thallus is no indication of colorific power (in
orchil lichens), inasmuch as the red or purple colouring substances are the
result of chemical action on crystalline colorific "principles" previously
devoid of colour.
3. That alterations in physical characters, chemical composition and
consequently in dyeing properties are very liable to be produced by modi-
fication in the following external circumstances :
(i) Degree of moisture.
(ii) Degree of heat.
(iii) Degree of exposure to light and air.
(iv) Climate.
(v) Elevation above the sea.
(vi) Habitat ; nature of basis of support.
(vii) Age.
(viii) Seasons and atmospheric vicissitudes, etc.
August has been recommended as the best month for collecting dyelichens
: i.e. just after the season of greatest light and heat when the
accumulation of acids will be at its maximum.
Some of the acids found useful in dyeing occur in the thalli of a large
number of lichens, many of which are too scantily developed to be of any
economic value. Thus salazinic acid which gives the effective yellow-brown
dye in Parmelia conspersa was found by Zopf in 13 species and varieties.
It has since been located by Lettau 2 in 72 different lichens, many of them,
however, with poorly developed or scanty thalli, so that no technical use
can be made of them.
S. L.
1
Lindsay 1855.
2 Lettau 1914.
2 7