FLOWERS AND INSECTS: Their Re lations. The lower plants are dependent upon water for the accomplishment of fertilization in the course of their sexual reproduction. They possess nothing in the nature of flowers and are independent of insects. It is impos sible now to determine whether the first plants with true flowers were of such nature that insects served for pollination. In view of the present rather generally accepted belief that the first flowers were of a type represented now most closely by the magnolia, it seems probable that the mutually beneficial interrela tions of flowers and insects began at an early date in the development of the flowering plant phylum. The simplified flowers of grasses, sedges, pigweeds, oaks, elms and other plants dependent upon wind for pollination are now seen clearly to be descended from flower types of a more showy nature that were in sect-pollinated.
The insects are benefited in this relation by the food that they obtain. This is of two kinds, nectar and pollen. It is probable that the first insect visitors of flowers, ages ago, were pollen gatherers which used the pollen for food just as many insects do now. Later, probably, came the production of nectar by the flower; a lure that is attractive to still larger numbers of insects and that saves to a certain extent the precious pollen. The additional lure of special odors was presumably developed at about the same time. The development of bright or showy colors on the flowers them selves or on adjacent bracts to attract the in sects by the sense of sight must have taken place rather early also, but the fossil records are so imperfect that the exact period cannot be determined. It is unfortunate that as a whole the flower is rather poorly adapted for preservation as a fossil, and especially such delicate parts as petals, stamens, nectanes, etc. Consequently we know more about the struc ture of the reproductive cones of the fossil Bennettitales, which are considered to be the forerunners of flowers than we do of the ear liest true flowers themselves.
The earlier investigators of the relations of Insects to flowers, such as Sprengel, Darwin and Hermann Muller, laid perhaps too much stress upon the value of the bright coloration of the flowers as a lure for insects. There is no doubt that a great many insects are i guided to the flowers by the sense of sight. Thus it is noteworthy that night blooming flowers are usually large and white, thus being more con spicuous than if of any other color. On the other hand it must be admitted that the large amount of perfume given off by such flowers cannot fail to attract night flying moths and other insects, even from great distances, until they are near enough to see the flowers. This is probably the case, too, with many day bloom ing species. The work of Plateau, in Belgium, and of others has shown that if the odors be present many insects will continue to visit flowers, even if they are so mutilated by the removal of petals and other showy parts as to be comparatively inconspicuous. Possibly some groups of insects pay no attention at all to the shape or color of the flower but are guided solely by the odor. On the other hand the existence of (to us) odorless flowers which are very showy and freely visited by insects would seem to indicate that the colors are of advan tage. Indeed, experiments with differently colored pieces of cloth, all scented in the same way so as to be attractive to insects, demon strated that although the amount of odor for each piece was the same yet the brighter col ored pieces actually drew more insects from a distance than the dull or inconspicuous pieces. The fact that some inconspicuous flowers that are nectariferous and sweet scented are freely visited by insects demon strates that however advantageous it may be to have showy flowers to allure the insects, still that is not an absolutely indispensable feature.