PREFACE. 



The 12 parts which form this volume comprise 19 different papers. 

 The first of these, by William R. Maxon, is the second of a series 

 designed as a convenient means of bringing together the results of 

 his studies of tropical American ferns, of which the National Museum 

 has acquired large collections within recent years. In his report 

 upon Baron von Turckheim's recent Guatemalan collections Mr. 

 Maxon directs attention to the lack of adequate material from the 

 humid region of eastern Mexico. This deficiency exists not only in 

 the case of the ferns and allied plants, but to a largo extent in that 

 of the phanerogams as well. It is to be hoped that means may 

 be found to carry on in this region botanical exploration of the same 

 character and extent as that which has been devoted in recent years 

 to the plateau of Mexico. We shall then have a thorough knowledge 

 of the flora of the low humid region, instead of an imperfect knowl- 

 edge resting largely on collections of half a century or more ago. 



The second number, consisting of a paper prepared by Dr. 

 J. N. Rose in cooperation with J. A. Purpus, of the Darmstadt 

 Botanical Garden, Germany, contains the descriptions of three 

 interesting new species of Echeveria from southern Mexico. The 

 beauty of two of these is such as to warrant their introduction into 

 ornamental cultivation along with many other beautiful and 

 striking species of Echeveria which have been discovered in 

 Mexico during the last few years. 



The grasses of Alaska, treated in part 3, arc of great interest, not 

 only from the standpoint of technical botanical science, but because 

 they form one of the great natural resources of that region, as yet 

 little utilized. Although many lists of grasses from Alaskan localities 

 have been published, no comprehensive and critical work on the whole 

 subject exists. The present paper, prepared by Prof. F. Lamson- 

 Scribncr and Mr. Elmer D. Merrill, brings our knowledge up to date 

 and will serve as a working basis for the study of Alaskan grasses 

 until that vast region has been more fully explored and its vegeta- 

 tion more thoroughly investigated. 



Part 4 is the second paper of a series by Henry Pittier, of the 

 Department of Agriculture, entitled Now and Noteworthy Plants 

 from Colombia and Central America, the first having been published 

 in volume 12 of the Contributions from the United States National 

 Herbarium, pages 171 to 181. It consists chiefly of descriptions of 



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