More advanced flowers escaped from such dependence on chance by no longer relying on deceit, trapping, and tasty pollen alone; nectar became increasingly important as a reward for the pollinators. Essentially a concentrated, aqueous sugar solution, nectar existed in certain ancestors of the flowering plants. In bracken fern even nowadays, nectar glands (nectaries) are found at the base of young leaves. In the course of evolutionary change, certain nectaries were incorporated into the modern flower (floral nectaries), although extrafloral nectaries also persist. Flower colours thus seem to have been introduced as “advertisements” of the presence of nectar, and more specific nectar guides (such as patterns of dots or lines, contrasting colour patches, or special odour patterns) were introduced near the entrance to the flower, pointing the way to the nectar hidden within. At the same time, in a complex pattern of parallel evolution, groups of insects appeared with sucking mouthparts capable of feeding on nectar. In extreme cases, there arose a complete mutual dependence. For example, a Madagascar orchid, Angraecum sesquipedale, with a nectar receptacle 20 to 35 cm (8 to 14 inches) long, depends for its pollination exclusively on the local race of a hawkmoth, Xanthopan morganii, which has a proboscis of 22.5 cm (9 inches). Interestingly enough, the existence of the hawkmoth was predicted by Charles Darwin and Alfred Russel Wallace, codiscoverers of evolution, about 40 years before its actual discovery.
