[ UNIVERSITY 



V OF 



X 



WASHINGTON ACADEMY OF SCIENCES 



VOL. VI, PP. 1-202. SEPT. 10, 1904, 



CONTRIBUTIONS TO THE KNOWLEDGE OF THE 



LIFE HISTORY OF PINUS WITH SPECIAL 



REFERENCE TO SPOROGENESIS, THE 



DEVELOPMENT OF THE GAMETO- 



PHYTES AND FERTILIZATION. 



BY MARGARET C. FERGUSON, PH.D., 

 ASSOCIATE PROFESSOR OF BOTANY, WELLESLEY COLLEGE. 



PLATES I-XKIV. 



CONTENTS. 



Introduction. 



Purpose of the study 3 



Historical notes 5 



Methods. 



Collecting 12 



Fixing 13 



Staining 15 



CHAPTER I. Microsporogenesis. 



The microsporangium. 



The wall of the pollen-sac 17 



The primitive archesporium 18 



Tetrad-division. 



The definitive archesporium 20 



The first nuclear division of the microspore-mother-cell 21 



The second mitosis of the mother-cell 30 



The problem of reduction 31 



Development of the microspore. 



The formation of the spore-wall 34 



The origin of the air-sacs and liberation of the microspore .... 36 



The growth of the microspore 37 



Summary 39 



Proc. Wash. Acad. Sci., September, 1904. (i) 



