PREFACE. j x 



Eu.)": those adventive, or imperfectly naturalized from Europe, by the 

 phrase " (Adv. from Eu.)," &c. 



Such varieties asare marked and definite enough to require names are 

 distinguished in this edition into two sorts, according to their degree of ap- 

 parent distinctness : — 1 . Those which, I think, can hardly be doubted to 

 be varieties of the species they are referred to, at least by those who hold 

 sound views as to what a species is, have the name printed in small capi- 

 tals; e.g. Nasturtium palustre, var. iiispidum, p. 30; Vitas cordifolia, 

 var. riparia, p. 78. 2. Those so peculiar that they have not only for the 

 most part been taken for species, but may still be so regarded by many 

 most excellent botanists ; some of them I may myself so regard hereafter, 

 on further and more critical examination of the apparently connecting 

 forms. The names of these are printed in the same full-face type as those 

 of the indigenous species (e. g. Ranunculus aquatilis, var. divaricatus, 

 p. 7; Aetata spicata, var. rue Sua, and var. alba, p. 14) ; and they usu- 

 ally stand at the head of a separate paragraph. 



Another important feature of the present edition consists in the plates, 

 fourteen in number, crowded with figures, illustrating the genera of the six 

 Cryptogamous Orders (Mosses, Ferns, &c.) embraced in the work. The 

 eight most elaborate and admirable plates illustrating the Mosses and Liv- 

 erworts are furnished by my generous friend, Mr. Sullivant, the author 

 of that portion of this work.* The remaining six plates, devoted to the 

 Ferns and their allies, were drawn from nature, and executed by Mr. 

 Isaac Spkaguk. 



Mr. Sullivant has included in this edition all the species of Musci 

 and Ilepatkce known to him as natives of any part of the United States east 

 of the Mississippi, and has sedulously elaborated the whole anew; not only 

 laying a broad foundation for a knowledge of North American Muscology, 

 but furnishing botanical students with facilities for the study of these two 

 beautiful families of plants such as have never before anywhere been 

 afforded in a book of this kind.f 



* The illustrations of forty of the genera, as indicated in the Explanation of the Plates at 

 the close of the volume, are entirely original productions of Mr. Sullivant's pencil. Seven of 

 them represent new species, and for most of the others those species were chosen which have 

 before been only imperfectly if at all figured. The rest of the genera were taken from Schim- 

 per, Bischoff, or Hooker, but ameuded or altered in accordance with the object in view and 

 the suggestions of an actual examination of the plant, which was always made. 



t The reference " Muse. Bar -Amer.," appended to many new or rare Mosses, is made to an 

 almost complete arranged collection of the Musci and Hepaticai east of the Mississippi, the 

 types in great measure of the present elaboration of these families, all critically studied by 

 Messrs. Sullivant and Lesquereux, and published in sets of specimens by the latter. 



The materials from which these sets have been prepared are chiefly Mr. Lesquereux's own 

 very extensive collections, the result of his numerous journjys made during the last six or 

 seven years, especially in the southern ranges of the Alleghany Mountains. To these have 

 been added Mr. Sullivant's ample accumulations, embracing the collections of the lamented 



