We will first confine our attention to the yield per acre. This has already been shown to depend on the presence in the soil of plenty of the various elements required by plants, in the case of wheat nitrogen being especially important. The need of suitable soil and proper cultivation has also been emphasised. These conditions are to a great extent under the control of the farmer, whose fault it is if they are not efficiently arranged. But there are other factors affecting the yield of wheat which cannot be controlled, such for instance as sunshine and rainfall. The variations in these conditions from year to year are little understood, but they are now the subject of accurate study, and already Dr W. N. Shaw, the chief of the Meteorological Office has suggested a periodicity in the yield of wheat, connected with certain climatic conditions, notably the autumnal rainfall. We have left to the last one of the most important factors which determine the yield of wheat, namely, the choice of the particular variety which is sown. This is undoubtedly one of the most important points in wheat-growing which the farmer has to decide for himself. The British farmer has no equal as a producer of high class stock. He supplies pedigree animals of all kinds to the farmers of all other lands, and he has attained this preeminence by careful attention to the great, indeed the surpassing, importance of purity of breed. It is only in recent years that the idea has dawned on the agricultural community that breed is just as important in plants as in animals. It is extraordinary that such an obvious fact should have been ignored for so long. That it now occupies so prominently the attention of the farmers is due to the work of the agricultural colleges and experiment stations in Sweden, America, and many other countries, and last but by no means least in Great Britain. This demonstration of the value of plant breeding is perhaps the greatest achievement in the domain of agricultural science since the publication of Lawes and Gilbert’s classical papers on the manurial requirements of crops.