26 ■ 



of these last two periods may be mentioned Eschweiler, Fie, Wall- 

 roth, Flogrke, Montagne and Schserer. Tuckerman began his stud- 

 ies under the influence of Acharius and Fries, and with Oakes and 

 Russell explored the White Mountains, and enumerated the New 

 England Lichens in the Boston Journal of Natural History. Muhl- 

 enberg, Eaton, Torrey, Halsey and Hitchcock collected and pub- 

 lished lists of Lichens. 



The microscope had up to this time been used to some extent in 

 the examination of Lichens, but with imperfect instruments, and lead- 

 ing to no important results. Fde had however figured the spores of 

 many Lichens in the supplement to his Essai sur les Cryptogames 

 des Ecorces Exotiques oflScinales, but he considered the theke as 

 the spore, and called the spores Sporidia. With the present period 

 and with better instruments began a closer microscopic study both 

 of the Thallus and of the Spores. De Notaris observed that the 

 spores of many genera were of a uniform type, and drew the con- 

 clusion that existing genera which included species having different 

 types of spores must be divided, and he established many new ge- 

 nera based on spore characters. Massalongo devoted a great deal of 

 labor to their study, and his- system in its subordinate parts is largely 

 based on spore differences. Koerber, although his system was based 

 on the Thallus distinguished as horizontal, fruticulose, and folia- 

 ceous, followed the Italian school in regard to the spores. Hepp 

 figured the spores of all the European lichens. New systems or 

 modifications of existing ones were proposed as knowledge advanced. 

 Norman, Theodore Fries, Montagne, Muller, Stitzenberger, Ny- 

 lander and others contributed their arrangements to the large num- 

 ber of preceding ones. Each prominent Lichenist has a system of 

 his own. 



Nylander, whose knowledge of Lichens, at least of individuals, 

 exceeds that of any other living Lichenist, has contributed more 

 largely than any other to the description of them. His system is 

 developed in his Synopsis Lichenum, which was intended to be to 

 the science of the present day what the Synopsis of Acharius was to 

 that of his time, but has not been continued since the first volume, pub- 

 lished in 1860. The system is eclectic, now giving the preference 

 to one, now to another part of the Lichen. He divides Lichens into 

 three families, the Collemacese, the Myriangiacese, and the Lichen- 

 acese. The claim of the second family to belong at all to the Li- 



