Chief among the travellers to whom we owe the acquisition of these favourite plants was Augier Ghislen de Busbecq, a Fleming, who was twice sent by the emperor as ambassador to the sultan. Busbecq was a keen observer and collector, and during his long and toilsome journeys was ever eager to pick up curiosities or to note new facts. Quackelbeen, a physician in Busbecq's suite, is named as another helper. The botanists Mattioli and Clusius, who presided in succession over the imperial gardens of Vienna, and Gesner of Zurich, described the plants; it is from them that we draw such imperfect knowledge as we possess of the way in which they were brought to central Europe. Clusius relates that Busbecq in 1575 received a parcel of tulip-seed from Constantinople, and being obliged to journey into France, left it with Clusius to be germinated. The tulips which came up were of various colours, an indication of long cultivation. The Turks, like the Persians, took great delight in gardens. As North America became permanently occupied by the English, facilities for the transport of live plants to Europe steadily increased. Ships began to sail frequently to and fro, for the crossing of the Atlantic was but a small affair in comparison with the voyage round the Cape of Good Hope. Educated men here and there practised the learned professions in the American plantations, and among them a sprinkling of naturalists was found. Hothouses, the amusement of wealthy amateurs in Germany, France, and Holland, made it possible to protect the plants of mild climates from the winter cold of northern Europe. By the end of the seventeenth century our gardens had acquired many beautiful and curious American plants, besides a few from the East Indies, and not long afterwards the gains became so frequent that the botanists of Europe found it hard to name the new species as fast as they came in.