The great point of Sprengel's discovery was in its being an intelligible explanation of the reason why flowers have bright colours, scent, and honey. At his time and indeed for many years afterwards, botanists looked on the stamens, petals, and other parts of the flower exactly in the way that a stamp collector looks at punctures and postmarks, that is without thinking about their meaning. Now we find that they are always designed to fulfil a perfectly definite purpose, and that all their details are contrived accordingly. This purpose is to carry the pollen from the stamens of one flower to the stigma of another. The pollen can usually be recognized as a yellowish or reddish dust formed in the stamens; this dust is generally rubbed off on an insect's proboscis or on part of its body. When the insect reaches another flower the pollen is scraped off by a sticky or gummy stigmatic surface. When the pollen has been placed on this surface it grows, germinates, and part of it unites with the egg-cell of the young seed. The latter is then, and not till then, able to become ripe and mature. It may be compared to cross-breeding in animals, though the process does not exactly correspond. But all flowers do not require insects to carry their pollen. In early geological periods we do not find any flowers like those that now exist, nor in those early times were there any flies, bees, or butterflies. The cockroach seems to have existed in Silurian (whinstone) times, and many gigantic and extraordinary insects lived in those damp forests of ferns, club-moss, and horsetails, of which the remains now form our British coalfields. Mayflies, plantbugs, and especially dragonflies (some of them with wings two feet across) existed, but none of these insects are of much use as pollen-carriers. Even much later on, when screw pines, monkey-puzzle trees, ginkgos, and bamboos formed the forests and woods of Europe, crickets and earwigs existed; but it is not until that geological period in which the chalk was formed (the Cretaceous age) that fossil plants like most of those now familiar to us occur. These had flowers intended for insects, and with the fossil plants we find the fossils of the insects that visited them. Bees, butterflies, and ordinary flies appeared upon the scene just as soon as there were flowers ready for them. Mr. Scudder has even found the fossils of certain plants, and with them the fossils of butterflies closely allied to the present butterflies which now live on present trees allied to those fossils! How then was the pollen of the first flowers carried?