194 



tains, an Essay on the Natural Systems of Oken, Fries, and Endlicher, 

 followed by a Preliminary View of the Structure and General History 

 of Lichens, and an Enumeration of North American Lichens, arranged 

 according to the Friesian system, giving the generic characters, but no 

 descriptions of the species. The list contains 238 species, but the au- 

 thor remarks that it is incomplete. 



His valuable Synopsis of the Lichens of New England, the other North- 

 ern States, and British America, was published at Cambridge in 1848. 

 It was and remains as yet the only full enumeration, with descriptions, 

 of North American Lichens, but is partially supplemented in writings 

 subsequently to be noticed. Its great value lies in the excellent de- 

 scriptions from Fries, on whose system it is based, and to the gene- 

 ral principles of which the author still adheres. It enumerates and 

 describes 295 species, of which about twenty are here first described. 



LEA'S Catalogue of the Plants of Cincinnati, Philadelphia, 1849, gives 

 a list of fifty-three species of Lichens, arranged by Professor Tucker- 

 man. AGASSIZ'S Lake Superior, published in 1850, contains a List of 

 Lichens collected in that region, including seventy-one species, also 

 arranged by Professor Tuckerman. 



The American Journal of Science for 1858 and 1859, contains two 

 Supplements to the Enumeration of North American Lichens, of the same 

 author. Sixty-six species, mostly new, from the Pacific coast, Cuba, 

 the Southern States, and New England, are. mentioned and described. 

 In the latter of these the spore-character is for the first time noticed. 

 In 1860, he contributed to the Proceedings of the American Academy 

 of Science and Arts (Boston), Vol. V, Observations on North American 

 and other Lichens, giving a review of the genera Physcia and Pyxine. 

 These observations were continued in Vols. V. and VI. of the same 

 work, published in 1862 and 1864. In them the author shows that he 

 had fully kept pace with the advance of the science, which by the appli- 

 cation of the microscope to the study of the internal structure, and the 

 development of the spores of Lichens, had assumed an entirely new 

 aspect since the era of the older Lichenists, who studied and wrote 

 withhout the aid of that instrument, now indispensable to all who 

 would make any certain progress in Lichenology, and which, while it 

 opens new difficulties, adds greatly to the fascinating interest of the 

 study. The last two of these papers are mostly occupied with descrip- 

 tions of the Lichens collected in Cuba by Mr. Wright, though quite a 

 number of New England and other continental plants are mentioned 

 and described for the first time. 



Professor TUCKERMAN also described the Lichens brought home by 

 the Wilkes Exploring Expedition, published in 1861, and accompanied 

 by admirable drawings of new species. The number of species men- 

 tioned is 104, of which four are new. 



