It must not be thought that European agriculture, before the great voyages of discovery, was stagnant as regards the introduction of new crops. The conquests of Alexander, the Arab invasions, the Crusades, had in turn familiarized Europeans with many exotic products. Since the beginning of the Christian era, introductions to Europe had included rice, sorghum, sugar-cane, cotton and several citrus fruits; amongst animals, the water buffalo and the silkworm had found an economic niche in southern Europe. Some of these introductions were still quite recent. Rice and cotton only reached Italy from Spain in the fifteenth century, and buckwheat was still spreading in France at the same time; hops, spreading slowly through northern Europe, were not planted in England till the early sixteenth century, when Englishmen first supplemented ‘ale’ with ‘beer’.

The Europeans of the fifteenth century were therefore well aware of the potential value of crop introductions. The group of crops in which their own agriculture was most deficient was the spices, which were in especially heavy demand in northern Europe where dried and salted foods perforce constituted so much of the diet in the winter months. To meet this demand, spices from Asia were imported overland at enormous expense. The conjunction of gold and spices in the quest of the early explorers is more understandable when we find Garcia da Orta recording in 1563 that 100 lb. of Ceylon cinnamon was worth 10 lb. of gold. Vegetable drugs were a subsidiary object of their quest; a medicine so much in esteem as rhubarb, for example, had to be imported from Asia and was quoted in France in 1542 as being ten times the price of cinnamon. Peres, the first Portuguese ambassador selected to go to China, where he arrived in 1517, was an apothecary who seems to have been expected to bring back useful plants.