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discovered in this country have since been found there. In the 

 Western district Lichens have been found similar to those of Africa 

 and South America ; and a number of European Lichens occur there 

 which have not been seen on the Eastern coast. One peculiar fea- 

 ture of that region is the tendency of many of the lower Lichens to as- 

 sume fruticulose forms, and to be prolonged downward into the earth, 

 exhibiting the finally ascendant tendency of the horizontal thallus. 



The stimulants of the growth of Lichens are moisture, heat and 

 light. But an excess of the first two is injurious, and tends to pro- 

 duce morbid and degenerate conditions. As they derive their sub- 

 sistence solely from the air, the nature of the soil is of minor import- 

 ance, but still not without its influence, especially on calcareous and 

 alkaline soils. Lichens are more abundant on the moist shores of 

 the continents than in thfe dryer interior. The perennial moisture 

 of portions of the Pacific coast is very favorable to their growth, 

 while the combined moisture and light of the tropics produces a 

 similar effect there. The Arctic region is poor in genera and spe- 

 cies, but rich in individuals, which afford food to animals, and in 

 times of scarcity even to man. The tripe de roche, on which Arctic 

 voyagers have supported life in time of need, is an Umbilicaria ; but 

 it is not a wholesome food, on account of the bitter principle it con- 

 tains, which may be partly removed by soaking in water. In recent 

 times the manufacture of alcohol from Cladonia rangiferina in north- 

 ern Europe has become quite an industry. Under proper treatment 

 Lichens yield a variety of colors, and they were formerly much used 

 in dying ; but modern chemistry has caused this use of them to be 

 almost entirely abandoned. They were also once supposed to pos- 

 sess considerable medical virtues. Peltigera canina was so called 

 because it was supposed to be a remedy for hydrophobia. Sticta 

 pulmonaria, from its resemblance to the tissues of the lungs, was 

 imagined to be a cure for consumption. But little or no importance 

 is pow attached to Lichens as remedies. 



The Lichens of calcareous rocks are usually different from those 

 of the granitic rocks. Some species are cosmopolitan, like Lecanora 

 subfusca and Usnea barbata, while others have a very restricted 

 range. Some species are exclusively corticoline, others saxicolous, 

 and others show no preference ; but lichens of either habitat may 

 often be found upon the other. Even Umbilicaria sometimes attaches 

 itseif to wood or bark. Verrucaria is exclusively saxicolous, and 



