INTRODUCTION. 



Lichens form a group of plants which has been 

 not so much overlooked and neglected as misunder- 

 stood and abused. The term lichen is rather un- 

 familiar, but not so the term " moss," by which the 

 plants here referred to are quite generally known 

 to layman as well as to poet. And, indeed, the term 

 moss is justifiable if we trace it to its Scandinavian 

 origin. All comparatively small thalloid cryptogams 

 — that is, flattened, stemless and flowerless plants — 

 were known as moss (most, mossa, moos, mus). The 

 term, therefore, included lichens, liverworts and mosses 

 proper. But from the present standpoint of science 

 lichens are not mosses, as will be made clear later ; 

 lichens are an independent group of plants having no 

 genetic relationship to mosses. 



Nor must it be supposed for a moment that lichens 

 are uninteresting and insignificant. With the one ex- 

 ception of marine algae, no plants present such truly 

 beautiful and artistic features to the amateur in nature- 

 study. No group of plants is so easily obtainable or 



