1903-1904-] A Short Talk on Lichens. 87 



has offered a prize in October of this year for the best col- 

 lection of lichens of the Edinburgh district, my purpose will 

 be served if I excite some interest in this study and induce 

 some members to compete. 



The study of lichens is one of the most difficult in botany, 

 and even at the present day, after many years of careful ob- 

 servation by very competent authorities, many points as to 

 their chemistry, the functions of some of their organs, and 

 their life -history, have not been satisfactorily solved. To do 

 justice to their study very minute and careful microscopic 

 work is necessary. No vegetable productions are more liable 

 to variation, and without a knowledge of the fruit it is almost 

 impossible to distinguish species accurately. The number of 

 species of British lichens is about 1710. The popular names 

 of some of them are cup-moss, old man's beard, Iceland moss, 

 rock-hair, lung- wort, cud-bear, stane-raw, orchil, reindeer moss, 

 earth-bread. Tripe de roche, rock-moss, dog-lichen, &c. 



Lichens occur everywhere, growing upon the most unlikely 

 substances, as cooling lava, the hardest quartz, naked glass, 

 coral reefs, in arctic regions, above the snow-line, in tropical 

 forests, on the arid desert, the sea-shore, bark of trees, and 

 even on living leaves, and some are parasitic on others. No 

 lichens, however, are entirely aquatic. They form the very 

 outposts of land vegetation, and are the first forms of vegeta- 

 tion, preparing and disintegrating the soil for higher forms of 

 plant life. They shun places where the atmosphere is delete- 

 rious and also the dark recesses of tropical forests. They are 

 able to resist an amount of heat and cold which would be 

 fatal to more organised plants. They increase in abundance 

 towards the arctic regions, but in number of species towards 

 the equator. 



The economic uses of lichens are various. They are used 

 as dye-stuffs, food for man and beast, in medicine, for per- 

 fumery, &c. Among dyes from lichens we have orchil from 

 Eoccella tinctoria ; litmus from orchil, cud-bear, &c. Lecanora 

 tartarea, a native lichen, is nearly equal to orchil as a dye- 

 stuff. In short, this property of affording colouring - matter 

 is more or less characteristic of the whole tribe of lichens. 

 Some without any visible colouring - matter nevertheless 

 contain colouring principles which yield beautiful tints when 



