vi PREFACE 



In compiling my materials I must acknowledge the immense help 

 which I received from the writings of the late Professor K. Schnarf, 

 whom I came to know rather intimately during my stay in Vienna 

 in 1936. Without the existence of his books, entitled "Embryologie 

 der Angiospermen" (1929), "Vergleichende Embryologie der Angio- 

 spermen" (1931), and "Vergleichende Zytologie des Geschlecht- 

 sapparates des Kormophyten" (1941), my task would have been 

 appreciably greater. Mention must also be made of the numerous 

 and very valuable publications of Professor E. C. R. Soueges (Paris), 

 Professor K. V. O. Dahlgren (Uppsala), Dr. J. Mauritzon (Motala), 

 Dr. F. Fagerlind (Stockholm), Dr. A. Gustafsson (Svalof), and 

 Dr. H. Stenar (Sodertalje), upon which I drew rather freely. Pro- 

 fessor Dahlgren, Dr. Gustafsson, and Dr. Stenar also favored me 

 with their advice and criticisms whenever I applied to them for 

 help. In addition, a host of teachers and students in the United 

 States gave me every possible encouragement in the work. To 

 record my gratitude to all of them in any complete fashion would 

 fill several pages. I therefore content myself with naming a few 

 who took special interest in the project. To Professors R. H. 

 Wet more and I. W. Bailey I am heavily indebted for the free use of 

 their facilities and their assistance in other ways during my several 

 months' stay at Harvard. Professor A. F. Blakeslee and Mary E. 

 Sanders, Smith College, Northampton; Professor E. W. Sinnott, 

 Yale University; Professors A. J. Eames and L. W. Sharp, Cornell 

 University; Drs. D. C. Cooper, R. A. Brink, and C. L. Huskins, 

 University of Wisconsin; Dr. Th. Just, University of Notre Dame, 

 now at the Field Museum of Natural History, Chicago; Professor 

 J. T. Buchholz, University of Illinois; Professor A. S. Foster, Pro- 

 fessor G. L. Stebbins, Mrs. M. S. Cave, Drs. L. Constance, Katherine 

 Esau, and C. M. Rick, all of the University of California; Pro- 

 fessor G. M. Smith, Stanford University; Dr. D. A. Johansen, Po- 

 mona, and Professor A. W. Haupt, University of California at 

 Los Angeles, gave me the benefit of their suggestions and criti- 

 cisms. Last but not least, my colleagues and pupils, Dr. B. M. 

 Johri, Reayat Kahn, S. Narayanaswami, and J. S. Agrawal gave 

 me their fullest cooperation in the preparation of the bibliography 

 and revision of the proofs. 



Only a few of the illustrations are original, most of them having 

 been borrowed from the works of other authors. Considerable 

 care has been exercised, however, in their selection not only that tht 



