 During her graduate studies and postgraduate appointment as a botany instructor , McClintock was instrumental in assembling a group that studied the new field of cytogenetics in maize . This group brought together plant breeders and cytologists , and included Marcus Rhoades , future Nobel laureate George Beadle , and Harriet Creighton . Rollins A. Emerson , head of the Plant Breeding Department , supported these efforts , although he was not a cytologist himself . 
