A MORPHOLOGICAL STUDY OF THE FLOWER 



AND EMBRYO OF THE WILD OAT, 



AVENA FATUA L. 



BY WILLIAM AUSTIN CANNON, 

 Assistant in Botany, Leland Stanford Junior University. 



CONTENTS. 



Plates XLIX-LIII. 



Page. 



I. Introduction 329 



II. Origin of the Floral Organs 33i 



III. The Stamen 335 



IV. The Embryo-sac 337 



V. Fertilization and the Building of the Endosperm 342 



VI. The Embryo 343 



VII. Summary 35i 



Bibliography 354 



Explanation of Plates 35^ 



I. Introduction. 



The grasses are said by Hackel to be a very isolated 

 family, sharply defined from the other low Monocotyledons 

 to which they are bound by only obscure relationships. 

 For this reason they have been variously placed by systema- 

 tists, but are now generally and probably best regarded as 

 near the Aroids and the Palms. The life history of such 

 grasses as have been studied justifies this conclusion, and it 

 is the object of this investigation to add something to our 

 knowledge of these forms in order that their mutual relation- 

 ships may be better understood. Enough morphological 

 work has already been done on types alHed to the grasses 

 to form a basis for comparisons. It remains therefore only 

 for more extended and more thorough studies to be made 

 on grasses before comparisons can be instituted. There 

 have already been a few such studies published. The most 

 important recent contributions to our knowledge of the life 

 history of grasses have been by Lermer and Holzner ( 1888) , 

 and Koernicke (1896). The original of the former con- 

 tribution was unfortunately not at hand and I was obliged 



[329] April 14, 1900- 



