112 



FOOTNOTES FROM 



If we wish to obtain a true idea of the value and im- 

 portance of lichens in human economy, we must consider 

 them in perhaps the most singular of their aspects, viz., 

 as dye-stuffs and sources of colouring matter. Many of 

 the tree-lichens, in a moist state, are very showy, yield- 

 ing in water a coloured infusion corresponding to the 

 hue of their own leaves; but strange to say, these are 

 the least valuable species to the dyer. The lichens which 

 are richest in colorific principles, are crustaceous species 



FlG. 15. ROCCELLA TINCTORIA. 



growing on rocks, and utterly destitute of colour in their 

 natural state ; and it is one of the most striking triumphs 

 of chemistry as applied to the arts and manufactures, 

 that by its means some of the finest shades of red, purple, 

 and yellow are extracted from such unlikely substances. 

 The lichen popularly known as orchil (Fig. 15) affords 

 a remarkable illustration of the extent to which colorific 

 principles are developed in these outwardly hueless plants. 

 It derives its generic name Roccella from a Florentine 

 family called Eucellai, whose founder, for a long time a 



