18 EDITOR'S PREFACE. 



Lesquereux and Snllivant published tog'etlier the two editions of the 

 Musci Exsiccati Amerioani, the fir.st edition in 1856, the hist in 1865. The 

 Latin text of Sulhvant's Icones Muscorum was also largely written by Les- 

 quereux, and the publication of the second volume was carried forward 

 after SulHvant's deatli. 



For some years before his death, Snllivant had been engaged in col- 

 lecting materials for the publication of a complete account of the North 

 American moss Hora. After his death his extensive collections and library 

 were deposited in Harvard College Herbarium, and at the urgent request 

 of Dr. Asa Gray, Lesquereux was prevailed upon to take up and complete 

 the task. Much of this work Avas done before his sight failed him in 1869, 

 when it was necessarv to call in other assistance, and Prof. Thomas P. 

 James, of Cambridge, was interested in the work. He made such of the 

 microscopical examinations as had not been made, but his death again de- 

 layed the work, and it was not until 1884 that it was finally completed and 

 given to the world as a Manual of North American Mosses. 



His paleobotanical work is so extensiA^e and valuable, and is so well 

 known to all students of the science the world over, that little mention of it 

 is necessary here. His tirst work was published in 1854, and from that 

 year initil the day of his death the world saw issuing almost every year an 

 additional volume testifying to his indomitable energy and keen discrimina- 

 tion. He was a pioneer in the department of vegetable paleontology in this 

 country, and while some of the earlier work done, as is so commonly the 

 case in new and uuworked fields, will need revision when the fossil flora of 

 America is more thorougldy worked uj), the whole stands as a monument 

 which future generations may well marvel at and emulate. 



F. H. Knowlton, 



Assistant Paleontologist. 



U. S, Geological Survey, 



Washington, D. C, December 19, 1890. 



