LICHENS. 57 



plantations of covering the bark with moss, as a 

 substitute for lichens, and the bark thus mossed has 

 been found to produce a larger percentage of alka- 

 loids than unmosscd trees. 



Lichens are not popular objects, and their study 

 is almost absolutely confined to a few scientific men, 

 yet there are many reasons why a knowledge of them 

 should be more universally diffused. One writer 

 remarks that " if we consider that many species have 

 a texture which, by readily imbibing and eagerly 

 retaining moisture, renders them in a sense indepen- 

 dent of all climatal changes, enabling them equally 

 to brave polar cold and tropical heat ; that many not 

 only cling with such tenacity as to be inseparable 

 from, but can corrode or disintegrate the hardest and 

 barest rocks, even pure quartz ; that the most ample 

 provision has been made by the great Author of all 

 for their reproduction or multiplication, in spite of 

 the most adverse external circumstances, and under 

 conditions fatal to all higher vegetation, both by the 

 multiplicity and abundance of their reproductive cells 

 — which sometimes constitute almost the entire bulk 

 of the plant, — the extremely minute size and delicate 

 nature of those cells, by virtue whereof they arc 

 disseminated by every shower or zephyr, and the 

 readiness with which these germinate ; we cannot 

 fail to increase our surprise that a curiosity has not 

 been sooner awakened to become familiar with the 

 natural history of plants which strew the path of 

 man wherever he roams over the wide world — which 

 constitute the most universally diffused type of 

 terrestrial vegetation." To this one answer may be 



