PuEFAOii, 



It gives me pleasure to be able also to Introduce in this connection the 

 name of Dr. James W. Robbins, — a name long since enrolled among 

 American botanists. Our Flora has been recently in part reviewed by 

 him; and he has communicated to me, in relation to this work, the results 

 of his extensive and accurate observations, as will be seen by the frequent 

 recurrence of his name in the following pages. 



Grateful acknowledgments are also due to Dr. Joseph Barratt. He 

 Has kindly communicated his unequalled monograph of the willows, " Bail- 

 ees Americanae;" also that of the "Eupatoria verticillata ;" both of which, 

 abridged, I have adopted in this work. 



Among other friends and correspondents, from whom I have received 

 specimens and highly valuable information, and whose kindness will be 

 held by me in most grateful remembrance, are the following : viz. Dr. Al- 

 bert G. Skenner and Dr. John Plummer, Indiana; Dr. Samuel B. 

 Mead and Rev. E. Jenney, Illinois ; Mr. Wm. S. Sullivant, Professor 

 Locke, and Mr. Joseph Glare, Ohio ; Dr. I. A. Lapham, Wisconsin ; 

 Dr. Wm. Darlington, Pennsylvania ; President Hitchcock, Professor 

 Asa Gray, and Dr. Augustus A. Gould, Massachusetts; Mr. Tru- 

 man RiCKARD, New Hampshire; Dr. Sartwell and Mr. Brownne, 

 New York; Mr. S. T. Olney, Rhode Island; &c. &c. 



In the present edition, a chapter on the principles of Agricultural 

 Chemistry has been added to the "Elements," and some important alterar 

 tions introduced. The Flora has been to a great extent rewritten, and 

 enlarged, not only by the addition of such plants as were necessary to 

 adapt it to a wider section of country, as mentioned above, but by many 

 plants recently discovered within our former limits. At the end is appended 

 a synoptical view of the lower orders of the Cryptogamia, with their gen- 

 era ; and the whole Is now illustrated with numerous engravings. 



Finally, the present work is again submitted to the public with the assur- 

 ance that, on the part of the author, it shall still be his constant care to 

 detect and rectify its imperfections in future editions ; and with the earnest 

 hope that his labors may serve to awaken In the minds of others as deep 

 an interest in this branch of the study of Nature as they have done in 

 his own. 



LIeriden, N. H., April, 1847. 



In the present edition, the " Synopsis op the Natural System," pp. 

 131 — 136, is thoroughly reconstructed and much improved. 



