The progressive Middle Ages (about 1000 to 1500 A.D.) greatly increased the comfort of the wealthy and alleviated the miseries of the poor. We now hear of countries (England, the Low Countries, the western half of Germany, the northern half of Italy) where freemen cultivated their own land, or grew rich by trade, and these men were not content barely to support life. Under the later Plantagenets the wool-growers of that upland country which stretches from Lincolnshire to the Bristol Channel showed their wealth by building a profusion of manor-houses and beautiful perpendicular churches, many of which still remain. There can be little doubt that they were attentive to the rural industries which are so great a source of comfort and pleasure. In the sixteenth and seventeenth centuries the Flemings, a laborious and enterprising people, inhabiting a fertile country, excelled the rest of Europe in agriculture and horticulture. L'Obel, himself a Fleming, speaks with pride of the live plants imported into Flanders from Southern Europe, Asia, Africa, and America. By the close of the sixteenth century, or a few years later, the lilac, lavender, marigold, sun-flower, tulip, and crown-imperial, the cucumber and garden rhubarb, besides many improved varieties of native vegetables, were sent out from Flanders to all parts of Western Europe. During many generations English agriculture and horticulture, and not these alone, but English ship-building, navigation, engineering, and commerce as well, looked to the Low Countries as the chief schools of invention and the chief markets from which new products were to be obtained. Late in the sixteenth century a gentleman of the Vivarais (the modern Ardèche), named Olivier de Serres, wrote a book on the management of land,[5] which leaves a strong impression of the zeal for improvement which then pervaded Europe. De Serres was above all things intent upon extending silk-culture in France. On this topic he wrote with full knowledge, having reared silkworms for thirty-five years. The King, Henri Quatre, shared his hopes, and gave him practical encouragement. It is well known that a great industry was thus started; by 1780 the annual yield of silk-cocoons in France was valued at near a million sterling, while in 1848 it had risen to four millions. De Serres sought to promote the cultivation of the mulberry tree, not only because its leaves are the food of the silkworm, but because he believed that the fibres of the bast would be serviceable in the manufacture of cordage and cloth. He also tried to revive the ancient practice of hatching eggs by artificial heat. We learn from him that the turkey, recently introduced from Mexico, had already become an important addition to the poultry-yard, while maize from Mexico and beetroot from the Mediterranean coasts were profitable crops. Among the new appliances De Serres mentions artificial meadows, wind and water-mills, cisterns not hewn from stone, and greenhouses.