DEC 9 1899 



THE PROCESS OF FERTILIZATION IN ASPIDIUM 

 AND ADIANTUM.* 



Charles Thom. 



Introduction. 



The investigations of Ikeno, Hirase, Webber, and Shaw 

 have given increased interest and importance to all facts bear- 

 ing on the process of fertilization in plants. This interest 

 centers on those groups which mark the boundary line be- 

 tween the lower and the higher forms. The correspondence 

 between the results of Ikeno's work on Cycas revoluta and 

 those of Shaw on Onoclea makes necessary a close studj? of 

 the details of the fusion of the egg and spermatozoid for 

 related forms. Previous investigations in both animals and 

 plants have shown the spermatozoid as losing its distinct 

 character and assuming the form and appearance of a resting 

 nucleus of equal or nearly equal size with the nucleus of the 

 egg before their final fusion. Ikeno and Shaw, on the con- 

 trary, have described the actual entrance of an unchanged 

 spermatozoid nucleus into the nucleus of the egg which is 

 found in the usual resting stage. 



The work was begun in the Botanical Laboratory of Lake 

 Forest University under the advice and direction of Dr. R. A. 

 Harper, now of the University of Wisconsin. To him are due 

 the methods of work and much help and advice in the com- 

 pletion of it. The actual study of the material and all of the 

 work on the paper have been done in the Botanical Laboratory 

 of the University of Missouri during the college years '97-'98 

 and '98-99. To Dr. Ayers of the University of Missouri I 

 owe the daily assistance and inspiration which has enabled me 



* Presented to The Academy of Science of St. Louis by title, June 5, 

 1899. — A thesis presented to the Faculty of the University of the State of 

 Missouri for the degree of Ph. D., 1899. 



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