frequenting them occasionally carried adherent fructifying cells from one plant to another, and so aided fertilization; it would follow that anything which made such terminal clusters more attractive to such insects, or more conspicuous to them, or both, would further the multiplication of the race, and would so be continually increased by the extra multiplication of individuals in which it was greatest. Here we find the clue. This contrast of colour between the folia next to the fructifying parts and all other folia, must constantly have facilitated insect-agency; supposing the insects to have had the power of distinguishing between colours. That Bees and Butterflies have this power is manifest. They may be watched flying from flower to flower, disregarding all other parts of the plants. And if the less-specialized insects possessed some degree of such discrimination, then the initial contrasts of colour above described would be maintained and increased. Let such a connexion be once established, and it must tend to become more decided. Insects most able to discern the parts of plants which afford what they seek, will be those most likely to survive and leave offspring. Plants presenting most of the desired food, and showing most clearly where it lies, will have their fertilization and multiplication furthered in the greatest degree. And so the mutual adaptation will become ever closer; while it is rendered at the same time more varied by the special requirements of the insects and of the plants in each locality, under each change of conditions. Of course, the genesis of the sweet secretions and the odours of flowers, has a parallel interpretation. The simultaneous production of honey, or some kindred substance, is implied above; since, unless a bait co-existed with the colour, the colour would not attract insects, and would not be maintained and intensified by natural selection. Gums, and resins, and balsams, are familiar products of plants; apparently, in many cases, excreted as useless matters from various parts of their surfaces. These substances, admitting of wide variations in quality, as they do, afford opportunities for the action of natural selection wherever any of them, attractive to insects, happen to be produced near the organs of fructification. And this action of natural selection once set up, may lead to the establishment of a local excretion, to the production of an excretion more and more attractive, and to the disposal of the organ containing it in such a way as most to facilitate the carrying away of pollen. Similarly and simultaneously with odours. Odours, like colours, draw insects to flowers. After observing how Bees come swarming into a house where honey is largely exposed, or how Wasps find their way into a shop containing much ripe fruit, it cannot be questioned that insects are to a considerable extent guided by scent. Being thus sensitive to the aromatic substances which flowers exhale, they may, when the