This matter of seed-dispersal is of prime importance in our study of familiar British plantscapes, for our vegetation is the expression of the past and present efficiency of its particular rôle in the ever-changing drama of Nature. We shall do well to spend a little time in considering it. First of all, as to the nature of the seeds with which we have to deal. These are, as already pointed out, young plants, already a long way advanced from the egg stage, neatly tucked up and enclosed, in most cases along with a supply of food material, in a tight, strong skin, which is mostly of a particularly impervious character, protecting the young plant from injury by bruising, from attacks of small animal enemies, from extremes of heat and cold, of moisture and dryness. The young plant, too, is in a peculiarly resistant physiological condition. For instance, its breathing--or absorption of oxygen--is exceedingly slow, and it is not suffocated by burial, sometimes even for years, in the soil. And while the mature plant is killed instantly by immersion in boiling water or by exposure to a very low temperature, some seeds, if boiled for a quarter of an hour, are quite uninjured, while others, subjected experimentally to even the temperature of liquid hydrogen (-260° C., or 436 degrees of frost on our more familiar Fahrenheit scale), remain unaffected. Many seeds are liberated from the parent plant enclosed by or attached to appendages of various sorts (when they are called by the botanist _fruits_) which sometimes greatly aid dispersal, as in the Dandelion (_Taraxacum_), and sometimes appear to hinder it; in any case, while the young plant itself is usually quite small, it may, when surrounded by its food-supply and enclosed in its wrappings, be a bulky object--as is seen in the Cocoanut or Horse Chestnut. In the British flora, to which we may confine our attention, a crab-apple (containing a number of seeds), a hazelnut, and an acorn (each containing a single seed), are the largest _units of dispersal_ with which we have to deal. But these are quite exceptional in size, and the average seed (using that term in its original sense of the natural unit of dispersal) in the British flora does not exceed the size of a pin’s head. This remarkable reduction of size alone aids dispersal greatly.