FINK—THE LICHENS OF MINNESOTA. 35 
region. Some suggestion of this wonderful lichen growth may be 
seen in northern Minnesota, where patches may be found covering 
an acre or more of ground. Also in northern regions, both in America 
and Europe, other wild and domestic animals depend more or less 
upon these lichens for their food supply. 
Lecanora esculenta grows loosely attached to the rocks in high 
places in northern Africa, is carried long distances by the wind, and, 
falling in areas where food is scarce, is eaten by the inhabitants, 
both man and lower animals. This plant is supposed to have been 
the manna of the children of Israel. Nor is this the only lichen 
eaten by man, for Cetraria islandica, the well-known “ Iceland moss,” 
forms an important part of the food of the people of Iceland, as 
well as of their domestic animals. This Cetraria is especially rich in 
the peculiar starch-like compound so commonly built up in lichen 
tissues. Also some of our Gyrophoras and other common lichens, 
as Ramalina calicaris, Parmelia physodes, Peltigera canina, and Evernia 
prunastri (pl. 39, facing p. 203), have been used as food by man. 
The nutritive value of lichens is due mainly to the lichenin, or 
starch-like material. But there is a bitter substance found in the 
lichen which often gives an unpleasant taste and is irritating to the 
digestive tract. This may be removed by thorough washing in 
water or some alkali, after which the plants may usually be eaten 
with impunity. 
When grains or potatoes are at hand, the lichens may be powdered 
and mixed with these articles of food and a very palatable bread 
may be made. 
AS MEDICINAL AGENTS. 
A considerable number of lichens have been used for medicinal 
purposes, but few of the supposed medicinal properties have been 
able to stand the test of modern medical science. Thus the ‘dog 
lichen,’ our common Peltigera canina, was formerly supposed to be 
curative of hydrophobia, hence the specific name. Likewise Sticta 
pulmonaria was supposed to cure pulmonary diseases, while the well- 
known Usnea barbata was supposed to promote the growth of hair 
and to be a sort of cure-all. Evernia vulpina is said to have been 
used, mixed with other substances, to poison wolves. Lindsay, in his 
Popular History of British Lichens, states that Cetraria islandica 
furnished preparations which were to be found in the drug stores of 
England at the date-of publication of his volume, 1865, as curatives 
for dyspepsia, and we still find Cetraria given in our latest dispensa- 
tories as a remedy. It is the bitter principle of the lichens that 1s 
supposed to give them medicinal value, and it has been used in fevers, 
as a tonic, and as a purgative, as well as in the other ways men- 
tioned above. Also, alcohol has been made from lichens. 
