IV LETTER OP TRA NS.M PT TAT, 



cases the mder geographical range of known forms has been developed, as, 



for instance, the discover}-, in Arizona, of Ophioglossvm vulgatwm; and also 

 a number of rare species, as of the striking leafless tree of Arizona, the 

 Canotia, and specimens of which arc thus added to the Government and 

 other herbaria.. From the Agave plants a number are described as of value 

 for cordage and textile fabrics. The economic relations of various forage- 

 plants, native and introduced, are noted. The value of Chia (Salvia Colum- 

 baria) as a remedy and dietetic, as well as the medicinal qualities of other 

 plants, is defined. The present and prospective relations of the forests to 

 the settlement of the country receive mention, and tables prepared by Dr. 

 Loew of soil analyses at important points are introduced. 



Although investigations in Botany, governed in a measure by the 

 sparsely settled condition of the regions visited, are but incidental to the 

 systematic purpose of the Survey, which has for its main object the deter- 

 mination of data necessary for the construction of a detailed topographical 

 map, yet it is believed that the material here presented, as the result of 

 examination, by specialists, of large and complete collections, will have its 

 value as a substantial contribution to the knowledge of the Botany of 

 portions of the United States west of the 100th meridian and south of 

 the 40th parallel. 



Attention is invited to the authors of various parts of this report, whose 

 names appear on the title-page, and to whom so much is due for the skill 

 with which they have prepared their several parts, and a merited tribute to 

 the value of their services is hereby tendered. 



To Prof. Asa Gray, the veteran Botanist, to whom doubtful points 

 have been submitted, thanks are due. 



The zeal and fidelity displayed by Dr .1. T. Rothrock, not only in the 

 field, but in the preparation of his report, and in .superintending the colla- 

 tion of other reports, are worthy of all commendation. 



The excellent typographical work of the Government Printing Office 

 in the publication of the quarto reports of the Survey is worthy of men- 

 tion, while the artistic plate illustrations of this volume, furnished by Mr. 

 Julius Bien, of New York City, are creditable alike to his artistic taste and 

 the excellence of his establishment. The plates were drawn by the well- 



