IV PREFACE. 



In most cases the generic characters closely follow those given, 

 by Bentham and Hooker in Genera Plantarum. Some valuable 

 extracts from Bentliam will be found regarding the writings of 

 prominent authorities on grasses ; also notes regarding the tribes 

 and some of the genera. 



Besides the fine herbarium, of Michigan Agricultural College, I 

 have been permitted to examine all the grasses in the herbaria of the 

 University of Michigan and Harvard University (including the 

 grasses of the late Dr. Geo. Thurber), those of the Department of 

 Agriculture at Washington, and those of Professor Scribner. 



Prof. L. H. Bailey rendered some assistance in rejiorting tlie 

 geographical distribution of certain species ; Professor S. M. 

 Tracy furnished some notes on geographical distribution; L. H. 

 Dewey looked up a number of authorities and furnished notes con- 

 cerning a few species. A. A. Crozier rendered valuable assistance 

 in reading much of the revised proof. 



I have made an enormous number of measurements, usually 

 many from several plants for each species, and have recorded the 

 extremes. With rare exceptions the figures given are the results 

 of my own measurements. To familiarize readers with the decimal 

 scale here adopted, the jDublishers have placed a sheet in the back 

 part of this volume on which are ruled duplicates that may be cut 

 out and used to measure any part of a grass which is to be com- 

 pared with the text. 



Up to April, 1895, when the text was sent to the publishers, I 

 had described all species that I was able to obtain that were 

 native of the United States and northward; all those collected in 

 Mexico by C. G. Pringle and Dr. E. Palmer, but not the meagre 

 specimens of several of the older collectors in Mexico and Central 

 America. 



Heartily thanking every one who has rendered assistance and en- 

 couragement, this long-delayed volume is now subject to the in- 

 spection of all interested in the subject. 



W. J. BEAL. 

 Agricultukat. College, Mich., 



September, 1896. 



