GINKGOALES 201 



with one or more parenchyma cells between. Miss Carothers 

 counted 8 as the x number of chromosomes. Sprecher did not 

 determine the exact number, but estimated that it was not less than 

 7 or more than 10. 



By the end of April, a pollen chamber has been formed by the 

 breaking down of cells at the apex of the nucellus. Some of the 



Fig. 216. — Ginkgo biloba: A, section of young ovule, showing nucellus and integu- 

 ment, April i; B, section of pair of ovules; C, megaspore mother-cell surrounded by 

 spongy tissue. May i. A, Xi5;j5, Xi2;C, X32S. — After Carothers.'" 



broken down material is mucilaginous and is exuded, appearing just 

 outside the micropyle as the pollination drop. Pollen, caught in this 

 drop, is drawn down into the pollen chamber and is sealed in by the 

 drying of the drop. The further development of the pollen chamber 

 and other parts of the ovule is doubtless stimulated by the presence 

 and development of the pollen. 



The ovules increase rapidly in size, maintaining a mottled pea- 

 green color. One of the two ovules on each peduncle usually aborts; 

 but when conditions are favorable, it is not at all uncommon for 

 both ovules to develop into good seeds (fig. 214). 



