2 GUIDE TO THE STUDY OP LICHENS. 



rius to De Notaris (1845) ; 6, from De Notaris to 

 1867. In my *' Text-book of General Lichenology" 

 I have retained Krempelhuber's limitations of the 

 first three periods ; the others have been changed, 

 and the review has been completed to the beginning 

 of 1897. As thus modified, the fourth period is from 

 Weber to Wallroth and Meyer (1825), the fifth from 

 Wallroth and Meyer to Schwendener (1868), the 

 sixth from Schwendener to Reinke (1894), and the 

 seventh beginning with Reinke. The reasons for 

 the changes will become evident upon the considera- 

 tion of the historical review as here given. 



For the purposes of a very brief review it was 

 thought best to recognize two grand periods. Only a 

 few of the more important workers in lichen ology will 

 be mentioned. At the present time the publications on 

 lichens number many thousands ; to collect and digest 

 these is the work of years. The beginner will, how- 

 ever, feel somewhat relieved to learn that of the 

 thousands of publications on lichens only a compara- 

 tively few are of any intrinsic value or add to our 

 knowledge of the subject. 



I. FROM THE EARLIEST TIME TO WALLROTH AND 

 MEYER (1825). 



This may be characterized as the period in which 

 no real scientific study was made of lichens. The 

 botanical systematists of the time devoted their at- 

 tention to the higher plants, especially those of real 

 or imaginary economic value. The lower plants 

 were quite generally neglected, lichens in particular. 



