PHYSIOLOGY OF CORN PLANT 53 



which penetrates the silk ; and soon the contents of the 

 pollen-grain pass down to the egg, in the embryonic seed 

 at the base of the silk. Immediately upon fertilization, 

 the ovule begins a rapid growth. In case a part of the 

 silk should fail to receive pollen, those ovaries will not 

 develop, and the result will be irregular rows on the ear. 

 Sometimes in very hot and dry weather the pollen is 

 killed and will not fertilize. Also, insects such as grass- 

 hoppers often eat off the silks, or a part of them, thus 

 preventing fertilization. 



Several investigators have studied fertilization and embryonic 

 development of the corn ovule, as Guignard, Webber, True, and 

 Poindexter. No one has reported observing the passage of a 

 pollen-tube down the silk. There is some question as to whether 

 the pollen-tube actually passes down within the tissues of the 

 style, or whether it may not follow the slight depression or 

 groove on one side of the style. Guignard calls the opening near 

 ^he base of the style the " stylar canal," and thinks that the pol- 

 len-tube enters this opening, but he did not observe it. When 

 the ovule is finally reached, it has not been definitely observed 

 at just what point the pollen-tube enters. 



Tbue, Rodney. Bot. Gaz. 18 : 215. 



Poindexter, C. C. The Development of the Spikelet and Grain of 

 Corn. The Ohio Nat., Vol. IV, No. 1, Nov. 1903. 



