INTRODUCTION. 



Asa Gray's first scientific paper was published in 1834 ; 

 his last was written in 1887, a few weeks before the end of his 

 life. The number of his contributions to science and their 

 variety are remarkable, and astonish his associates even, 

 familiar as they were with his intellectual activity, his vari- 

 ous attainments, and that surprising industry which neither 

 assured position, the weariness of advancing years, nor the 

 hopelessness of the task he had imposed upon himself, ever 

 diminished. 



Professor Gray's writings may be naturally grouped in four 

 divisions. The first in importance contains his contributions 

 to descriptive botany. These with few exceptions were de- 

 voted to the flora of North America, and although it did not 

 fall to his lot, as it did to that of some of his contemporaries, 

 to elaborate any one of the great families of plants, the extent 

 and character of his contributions to systematic botany will 

 place his name among those cf the masters of the science. 



His works of a purely educational character are only second 

 in importance to his writings on the flora of North America ; 

 and their influence upon the development of botanical knowl- 

 edge in this country, during the half century which elapsed 

 between the publication of the first and the last of the series, 

 has been great and must long be felt. No text-books of sci- 

 ence surpass them in the philosophical treatment of the sub- 

 jects they embrace, or in the beauty and clearness of their 

 style. 



A series of critical reviews of important scientific publi- 

 cations, and of historical accounts of the lives and labors of 

 botanical worthies, may be conveniently grouped in the third 

 division of Professor Gray's writings ; while in the fourth fall 



