NATIONAL ACADEMY OF SCIENCES. 



were new. Incomplete as it seems at the present time, it offered 

 to the student of that day the means of recognizing and referring 

 to their proper places in the then accepted system the more prom- 

 inent species of the eastern portions of the United States and it 

 served as an incentive to the study of lichens which was important. 

 As an adjunct to the synopsis should be mentioned the " Lichenes 

 American Septentrionalis Exsiccati," in three fasciculi, Cambridge, 

 1847-1855, including specimens of many of the species given in the 

 synopsis and collected mainly by Tuckerman himself. 



But the study of lichens soon assumed a new phase. The micro- 

 scopic characters began to be more carefully studied, new regions 

 were explored, and the number of observers increased rapidly. 

 Naturally, with the increase of collections and a more minute ana- 

 tomical study, not only did the older descriptive works prove inad- 

 equate but the systems of classification themselves required modifi- 

 cation. The Western explorers and a new generation of botanists 

 in the East amassed a large amount of material, while the various 

 expeditions to foreign lands brought home rich collections of lichens 

 which were placed in his hands for determination. From 1848 to 

 1872 he published numerous papers of which the more important 

 were a "Supplement to an Enumeration of North American Lich- 

 ens," in the Journal of Science in 1858 and 1859, where he described 

 many new species from the Southern States and California; Obser- 

 vationes Lichenologicre, in four parts, in the Proceedings of the Amer- 

 ican Academy, 1860 to 1877; the Lichens of the Wilkes Exploring 

 Expedition, and the Lichens of California, Oregon, and the Rocky 

 Mountains; Amherst, 1866. The second and third parts of the 

 Observationes related principally to species collected in Cuba, by 

 Charles Wright, and the range of his studies of exotic forms is 

 shown by the fact that, not including the papers previously named 

 which contained accounts of species from Eastern Asia, the Pacific 

 Islands, the Cape of Good Hope, etc., he also published papers on 

 species from Kerguelen's Land, the Hawaiian Islands, and Arctic 

 America. 



The elaboration of this rich material enlarged his views of classi- 

 fication and gave him a broad knowledge of generic types as well as 

 specific forms which he embodied in his " Genera Lichenum," pub- 

 lished at Amherst in 1872. This, it seems to the writer, should be 

 regarded as his greatest work. In it he displays a remarkable 

 knowledge of lichen forms and a thorough acquaintance with the 



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