From the point of view of the botanist, agriculture consists of the destruction of the plant associations which for some thousands of years have occupied the ground, and their replacement by other plants which are useful to man. The natural plant associations being the result of the survival of the fittest through a long period of time, while the farmer’s crops represent plants which do not grow naturally on the ground, nor often indeed in the country (while they are frequently artificial forms unable to reproduce themselves), it follows that the latter cannot compete with the former, and can be maintained only by the most careful protection. The native plants are always striving to reoccupy their legitimate territory, and the farmer is incessantly engaged in trying to keep them out. Agriculture, indeed, has been defined as “a controversy with weeds.” Incidentally, the suppression of the natural flora allows many weaker plants an opportunity of which they are not slow to take advantage. These may be natives, but are often annuals which have followed the spread of farming operations, or which are directly--though unintentionally--introduced by man as impurities in the seed which he sows. Let us look a little more closely into the question of profit and loss in our flora resulting from agriculture. In the first place, whether the ground is tilled or grazed, the woodland which primitively occupied so much of it disappears. The plough and the scythe are fatal to all seedling trees. Little less fatal is the browsing of cattle and sheep, and even in rough pasture only thorny plants like Whitethorn and Gorse may be found battling successfully for a lodgment. Where woodland is used for pasturage, the delicate shade plants--Anemones, Wild Hyacinths, Primroses--soon die out. No young trees appear on the grazed surface, though hundreds of thousands of seeds may be shed annually over the ground. In the course of time the present trees will die, and only grass remain. How different is it where cattle are excluded and the scythe unused! Among the grass young trees spring up everywhere, and in the woods a dense undergrowth of saplings sheltering a varied shade flora makes its appearance; regeneration of the natural woodland proceeds apace.