The book was dedicated to his longtime friend and colleague, Harvard botany professor Asa Gray "as a small tribute of respect and affection".
Darwin’s reflections indicate the economy of nature through a process of gradual modification of plants, their structures being modified and degraded for the purpose of the large scale production of seed which is necessary and advantageous for survival.
Darwin states (p. 227): "Cleistogamic flowers ... are admirably fitted to yield a copious supply of seed at a wonderfully small cost to the plant."
The same thing was found to occur in the primrose, as well as in flax (Linum perenne), lungworts (Pulmonaria), and a host of other plants, including the American partridge-berry (Mitchella repens).
The exact correspondence in the length of the style of each form with that of one set of stamens in the other form insures that the pollen attached to any part of the body of an insect shall be applied to a style of the same length on another plant, and there is thus a triple chance of the maximum of fertility....There is thus the clearest proof that these complex arrangements have the important end of securing both a more abundant and more vigorous offspring.” Observations and experiments still continue today to further the understanding of this phenomenon instigated by Darwin in this original and seminal work.