IV PREFACE. 



nomenclature. Mr. M. S. Bebb, of Eockford, III, has examined all our 

 Willows and revised the nomenclature, much of that part of the adden- 

 dum r efen-ing to th e Willows being his work. Messrs. Bennett and Beeby 

 have continued their work, and named our Potamogetons and Spargania. 

 We have been enabled to make the changes in, and additions to, the 

 genus Carex, by the use of Prof Bailey's Memoir, published by the 

 Torrey Botanical Club, und by his examination of our specimens col- 

 lected during the past two yeai-s. Prof P. Lamson Scribner has deter- 

 mined all the grasses collected in British Columbia in 1889, and other 

 critical species. The changes and additions in the order Grramineae, 

 are either his or have been made at his suggestion. Dr. T. J. W. 

 Burgess, our highest authority on Canadian Ferns, has prepared the 

 orders OphioglossaccEe and Filices. 



JOHN MACOUK 



Ottawa, May, 1880. 



