"310 Agricultural Experiment Station, Ithaca, N. Y. 



strongly curved and more or less twisted. In case the oogoninm 

 is a terminal one and possesses both a stalk antheridinm, and branch 

 antheridinm, the stalk antheridi'nn may curve so strongly to one 

 side as to make it difficult to determine later which is really the 

 stalk antheridinm. 



"While these changes are taking place in the antheridinm the 

 granular protoplasm of the oogonium is moving toward the center 

 to form the egg cell as described above, and now the end of the 

 antheridinm in contact with the wall of the oogonium, puts out a 

 slender tube which pierces the oogoninm wall, extends across the 

 space occupied by the periplasm and touches the egg cell at the 

 nearest point. This tube is known as the fertilization tube. At 

 this point on the egg cell there is a small clear space called the 

 receptive spot. 



Nearly all of the protoplasm in the antheridum except a very 

 thin layer next the wall becomes coarsely granular, arranged in 

 strings and is finally collected in the middle line of the antheridinm. 

 This is known as the gonoplasm, and soon passes through the fer- 

 tilization tube and is emptied into the egg cell at the receptive 

 spot, where it disappears in the substance of the egg cell and com- 

 pletes the act of fertilization. 



While the passage of the gonoplasm is going on it can be seen 

 that a thin wall is forming ai'ound the egg cell over the surface 

 ■except at the point where the fertilization tube is located. When 

 the gonoplasm has passed through, the wall becomes complete at 

 that point, and the entire wall then thickens somewhat and soon 

 becomes brown in color. The fertilized egg cell now becomes the 

 egg, or oospore. 



These phenomena in the development of the oogonia and an- 

 theridia and in the fertilization of the egg cell can be quite easily 

 followed by teasing out a small section of the diseased plant tissue 

 in water on a cover glass and arranging this for a cell culture in 

 what is known as a van Tiegham cell. This can be placed on the 

 stage of the microscope from time to time and the development 

 traced. From such a culture made from a diseased young melon 

 seedling the following record was made. The diseased tissue was 

 teased out in water on a glass slip Monday, January 28th, and placed 

 in a moist chamber. The following day, January 29th, a profuse 

 growth of mycelium, oogonia and antheridia had taken place, the 

 mycelium extending for 2mm to 3mm out from the diseased tissue. 



