396 SHERRET S. CHASE 



nation is that certain genotypes favor parthenogenesis. Whether this is a 

 function of the sporophyte or of the gametes is not certain. It appears more 

 likely that the efifect originates in the individual gametes (eggs). 



Emerson (unpublished) and Lindstrom (unpublished) and others have 

 attempted to stimulate parthenogenesis in maize by the application of hor- 

 mones and other chemicals to the ovules before or during fertilization. The 

 results were uniformly discouraging. Randolph (1932b) found a number of 



TABLE 25.3 



DISTRIBUTION OF MONOPLOIDS PER SEED 

 PARENT, STIFF ST.ALK SYNTHETIC 



Number of 



Monoploids Number of Seed 



per Seed Parents in 



Parent Each Class 



776 



1 195 



2 60 



3 19 



4 7 



5 3 



6 3 



7 2 



Total 1,065 



TABLE 25.4 



MONOPLOID FREQUENCIES AMONG THE 



PROGENIES OF MONOPLOID 



DERIVATIVES 



monoploids in material which had been subjected to heat treatments de- 

 signed to induce polyploidy. Though it is a question whether the heat induced 

 parthenogenesis, this type of treatment should be repeated on material in 

 which the natural rate of parthenogenesis is known. In connection with the 

 general monoploid study reported here a number of special treatments have 

 been tried. Among these are hormone treatments, X-radiation of pollen, 

 intergeneric crosses, pollination with pollen from tetraploid maize, and de- 

 layed pollination. These experiments are incomplete. 



There is presently available one method by which high rates of partheno- 

 genesis can be had. This is by selection of the pollen and seed parents used in 



