108 FOOTNOTES FROM 



of certain constituents which are extremely volatile, and 

 dependent upon such conditions. The lichen that de- 

 velops certain qualities when growing on the bark of a 

 tree, will not develop them to the same extent when 

 growing on a rock ; and there will be a similar, if not a 

 greater difference between the qualities of an individual 

 produced in the shade of a dark moist wood, and those 

 of the same plant, scorched by the sunshine and swept 

 by the wind on a bare exposed rock on the hill- side. It 

 was this variable chemical character, and the uncertain 

 medical results connected with it, that banished the 

 lichens from the druggists' shops. The discovery of 

 new and more powerful drugs, obtained from tropical 

 plants stimulated by intense sunshine and highly organ- 

 ized soils, hastened their exile, and effectually closed the 

 door against their return to favour ; while at the same 

 time it greatly diminished the list of native remedies, 

 the products of a cold, moist climate, and of poor and 

 feeble soils. The Iceland moss is the only species of 

 lichen which has retained its place in modern pharmacy, 

 as a tonic and febrifuge in ague ; but it is now princi- 

 pally employed, when added to soups and chocolate, as 

 a palliative to consumption, and as an article of diet in 

 the sick-room, and is being gradually superseded by the 

 more nourishing productions of foreign countries. 



It may seem strange that lichens should be employed 

 in perfumery, considering that in themselves they are 

 entirely destitute of odour, but such nevertheless is the 

 case. The ancients appear to have been in the habit of 

 using extensively a species of white filamentous lichen 

 called Usnech, which grew upon trees in the islands 



