Glucose, mannose, and fructose all form identical osazones. This is because the structure of these three sugars is identical except for the arrangement within the two groups at the aldehyde end of the molecule (see formulas on page 44). Since it is to these two groups that the phenyl hydrazine residue attaches itself, it follows that the resulting osazones must be identical in structure and properties. All other reducing sugars yield osazones of different physical properties.
If fertilization of all flowers were as simple as this, there would be no need of what follows, but actually in surprisingly few plants are the stamens and pistils so arranged, the ripening of the pollen and readiness of the ovule for impregnation so timed that the act can be accomplished in such direct fashion. For it is quite obvious that in flowers in which the whole drama of mating goes on within the petals, without the interference or help of any outside agency, the result will be a crop of young who know no other characters than those of the parents, and have nothing to look forward to but a closely inbreeding progeny, very little, if at all different from themselves.