VEGETABLE DYES 105 
habitats where no other vegetation could be supported, 
and the chief cost of production is the labour involved 
in collecting them. It is generally supposed that 
lichens grow too slowly to form a satisfactory crop; 
but planting experiments have never been system- 
atically tried. At any rate, a study in the field of the 
successions, in which these economic lichens form a 
conspicuous part, would be most interesting and might 
even prove profitable. 
Two series of dyes have been obtained from lichens. 
The beautiful purples and reds, sold as Orchil, Cud- 
bear, and Litmus, are obtained from various species of 
Roccella imported from the Canary Islands. The colour 
is developed by oxidation of the powdered lichen in 
ammoniacal liquor (obtained by the peasantry from 
stale wine, etc.). The fermentation takes some weeks, 
and the mass must be frequently stirred and kept at a 
moderate heat. After the oxidation the colour may be 
extracted. by alkalis, and the insoluble dye can then be 
precipitated as a reddish powder by any acid (acetic or 
hydrochloric acids are the ones generally used). The 
process can quite easily be carried out on test-tube 
scale with a lichen suspected of having tinctorial pro- 
perties ; allowing a week in o'880 ammonia for the 
oxidation stage. 
Although the colours, orchil, cudbear, etc., are not 
very permanent, they are of peculiarly beautiful quality, 
and are still used by dyers to impart bloom to compound 
shades. Similar dyes can be extracted from several of 
our native lichens, by analogous treatment. In Scot- 
land and the Shetland Islands Lecanora tartarea and 
Urceolaria calcarea were at one time collected in large 
