On the World's "Lichenes exsiccati". 



By 

 B. Lynge. 



M, 



.y object in writing these pages is to call attention to 

 a work whith I have in preparation, viz. an index of "Lichenes 

 exsiccati" throughout the globe. 



It is no easy task to define these collections — "Lichenes 

 exsiccati" — with exactitude. All authors agree that more than 

 one set is necessary, and that the specimens must be numbered. 

 The purpose of such collections is to enable the owners of sets 

 to profit by the results published by the specialist who has 

 examined the Lichenes of any one collection. It is therefore 

 obvious that a collection which has been issued, e. g. in 100 sets, 

 is of greater value than one consisting of very few sets. At the 

 same time I am unable to regard the number of sets as a deci- 

 sive factor in the definition of "Lichenes exsiccati". We cannot 

 say, with fairness, that if 10 sets have been issued, we have 

 "Lichenes exsiccati", but if there are only 9 sets we have not. 

 So long therefore as other requirements are fulfilled, I will in- 

 clude every collection that has been issued in more than one set. 



The method of distribution is also of importance. Some 

 authors are of opinion that the collections must necessarily be 

 sold, and that the purchaser is of no great importance. Yet 



