PDF - CES (IISc)

404
ECONOMIC AND TECHNICAL
These lichens are not bitter to the taste, nor are they irritating as are other
species of the genus. They are on the contrary quite harmless and are much
relished by the Japanese on account of their agreeable flavour, in spite of
their being somewhat indigestible. Though only determined scientifically in
recent times, this edible lichen has long been known, and the risks attending
its collection have frequently been described in Old Chinese and Japanese
writings.
Other species of Gyrophora including G. polyrhiza (Fig. 129) and
Umbilicaria, black leathery lichens which grow on rocks in northern regions,
Fig. 129. Gyrophora polyrhiza Koerb. (S.H., Photo, reduced).
have also been used as food. They are the "Tripe de Roche" or Rock Tripe
of Arctic regions, a name given to the plants by Canadian fur-hunters.
They have been eaten by travellers and others in desperate straits for food ;
but though to a certain extent nutritious, they are bitter and nauseous, and
cause severe internal irritation if the bitter acids are not first extracted by-
boiling or soaking.
Of more historical interest is the desert lichen Lecanora esculenta,
supposed to be the manna 1 of the Israelites, and still called "bread from
heaven." Eversmann 2 wrote an account of its occurrence and qualities, and
fuller information was given by Berkeley 3 : when mixed with meal to a
third of its weight it is made into bread and eaten by the desert tribes.
It grows abundantly in North Africa and in many parts of Western Asia,
on the rocks or on soil. It is
easily broken off and driven into heaps by the
wind; and has been reported as covering the soil to a depth of 15 cm. to
1 See p. 422.
2 Eversmann 1825.
3
Berkeley 1849.