vi PREFACE 



Agriculture, the seed illustrations being reproductions of 

 the unequalled drawings of Professor F. H. Hillman. 



The bringing together of the scattered results of Ameri- 

 can research with some references to those of Europe will, 

 it is hoped, reveal to students the phases of the subject 

 which need further investigation. 



In preparing this volume the author wishes to acknowl- 

 edge the aid he has received from his colleagues, B.. A. 

 Oakley, J. M. Westgate, H. N. Vinall, W. J. Morse, M. W. 

 Evans, H. L. Westover, and Katherine S. Bort. 



CHARLES V. PIPER. 



WASHINGTON, D.C., 

 January, 1914. 



