It was in all probability blown by the wind or carried in water. Even now poplars, alders, birches, and oaks rely chiefly upon the wind to carry their pollen. These plants were amongst the first of our modern flora to appear upon the earth. Some of them possess very neat contrivances suited to the wind. The catkins of the alder, for example, hang downwards, so that each little male flower is protected from rain by a little scale or bract above it. The pollen is very light, dusty, or powdery, so as to fly a long distance. The Scotch fir (Pinus sylvestris) has male flowers in little cones. These are upright, and the pollen of each stamen drops on to a small hollow on the top of the stamen below. It is then blown away by the wind on a fine dry day, but it is not allowed to get out in wet weather. It is said that vast clouds of pine pollen occur in America, and that the water of certain lakes becomes quite yellow and discoloured by it at certain seasons. Each little particle of pollen has two minute caps or air-balloons which give it buoyancy, so that it can float easily immense distances.
A curious little herb, the Wall Pellitory, and another foreign species, the Artillery plant, produces small explosions of pollen. When it is touched, there is a little puff or cloud of dusty pollen. Even the common Nettle does the same on fine dry days when it is in full flower.
But of course this carrying of pollen by the wind is a very expensive arrangement. It is so much a matter of pure chance that a grain arrives at its right destination. Suppose that a flower is giving out clouds of pollen, then the chance of a pollen grain reaching a female flower only five feet away is very small, even if the stigma of the female flower is a quarter of an inch in diameter. The chance of pollen reaching it will only be about 1 to 1440; 1439 pollen grains will be wasted[26] for every one that reaches the stigma. But even this is not quite a fair calculation, for if the female flower is not down wind, none will reach it at all!
But if an insect goes to the catkin of an alder or any other male flower, it will see the red points of the stigma and will very likely go there at once. This shows how much more reasonable and efficient insects will be.
The immense majority of flowers are, in fact, purple, blue, red, yellow, or white, so that they are conspicuous, and stand clearly out against the green of their leaves. It is well known to all who have arranged flowers for the table that the green of the leaves of different plants varies greatly in its shade and tint. Many greens do not match special flowers at all, but it is the fact that the green of any one plant is always quite harmonious, and agrees well with its own flowers!
Besides varied and beautiful colours, sweet or strong scents and supplies of honey or nectar are provided for insects.
How did flowers manage to produce all these attractions? No one has answered that question. We know in a general sort of way that the parts of flowers are modified leaves, and that petals and stamens become yellowish or pure white because they do not form green colouring matter like ordinary leaves.
It is also known that on the Alps or on any high mountain, where the air is pure and the sun strong, flowers become rich, brilliant, and vivid. In such places as the "Jardin" near Mont Blanc, the pure, deep, rich blue of gentians, the crimsons, reds, and purples of other flowers, impress the most casual and unobservant traveller. "White and red, yellow and blue, brown and green stand side by side on a hand's breadth of space." In that strong mountain air, also, perfumes are stronger, purer, and of finer quality than in the lowlands. There is a more intense, active, and vigorous life going on in flowers than is required by the more prosaic industries in other parts of a plant. Flowers also often live at a higher temperature than the surrounding air.
Kerner has described how the little flowers of Soldanella penetrate the snow by actually melting a passage for themselves through it (see p. [103]).
This high temperature and vigorous life, shown also by the rapid transpiration of flowers,[27] seems to hint that colours and perfumes appear in consequence of rapid chemical transformations.[28]