Here we have brought out very distinctly the effect of cross-fertilization in flowers, the result of grafting and the development of varieties. Better than that, we have here the recognition of that tendency in organisms to vary that lies at the very root of the development of species. Natural selection, survival of the fittest, were impossible were it not true that "Nature is made better by no mean but Nature makes that mean"; or, as it is more broadly stated a few lines further on, "This is an art which does mend Nature, change it rather, but the art itself is Nature." I consider these very remarkable statements when we reflect on the time in which they were written. Darwin, in 1860, does but unfold the thought. The selection which Shakespeare notes as practiced by gardeners, and a similar selection seen in the world of domestic animals, gave Darwin his cue of natural selection. The beauty of Darwin's thesis lies in the fact that the process is natural, and such is Shakespeare's dictum. Later on, lines 112-128, Perdita brings out another remarkable observation that has only lately been confirmed by the conclusions of science: "... Now my fairest friend, I would I had some flowers o' the spring that might Become your time of day; and yours; and yours; That wear upon your virgin branches yet Your maidenheads growing: O Proserpina, For the flowers now, that frighted thou let'st fall From Dis's wagon! daffodils, That come before the swallow dares, and take The winds of March with beauty; violets dim, But sweeter than the lids of Juno's eyes Or Cytherea's breath; pale primroses, That die unmarried, ere they can behold Bright Phoebus in his strength--a malady Most incident to maids; bold oxlips and The crown imperial; lilies of all kinds; The flower-de-luce being one!" Primroses are dimorphic--i. e., on the same species we find flowers of different sorts. These are complete, but in any particular flower the essential organs fail of adaptation to each other--the style in one too long, in another too short, to receive pollen from the stamens of its own flower. For fertilization such flowers are absolutely dependent upon the assistance brought by insect visitors. Perdita's primrose is _Primula veris_, the early primrose, "that takes the winds of March with beauty," and dies ere it beholds "bright Phoebus in his strength," and it is precisely this species that forms the basis of one of Darwin's earliest and most fruitful studies in the cross-fertilization of flowers. The styles in one form of the early primrose are three times as long as in the other, the stigmas differ, and the coadaptation of the parts of the different flowers extends even to the grains of pollen. Such flowers in the absence of insects are entirely unproductive. Insects are rare so early in the year, and accordingly many of the primroses die, as Perdita says, "unmarried."