Beginning of Essay
Mankind has selectively bred plants for thousands of years with the aim of improving their quality. Experimenting with cereal crops, breeders have aimed to enhance their yield of grain, the quality of their flour, and their resistance to disease and drought. Wit ....

Middle of Essay
.... with the hybrid variety, yielding twice as much corn. Plant breeders have a definite advantage over animal breeders, because they can often produce fertile varieties - indeed, new species - by crossbreeding between species. This is because hybrids are often polypoid. Polyploidy, as we know, can occur naturally in the wild. Some species of cotton that we grow are polypodies that probably arose originally by accidental crosses between different species of cotton. But breeders do not have to rely on accidents. They can attempt to produce fertile polypodies by crossbreeding between different species. One early attempt to produce anot ....