De l’Obel’s chief botanical work was the ‘Stirpium adversaria nova[14],’ published in 1570, with Pena as joint author. Pena does not appear to have been a botanist of much importance, and he eventually quite forsook the subject in favour of medicine. It has been suggested, however, that de l’Obel was inclined to minimise the value of his colleague’s work. The system of classification, upon which de l’Obel’s reputation really rests, is set forth in this book. The main feature of his scheme is that he distinguishes different groups by the peculiarities of their leaves. He is thus led to make a rough separation between the classes which we now call Dicotyledons and Monocotyledons. The details of his system will be considered in a later chapter. In 1576 the work was enlarged, and republished as the ‘Plantarum seu Stirpium Historia’; it was also translated into Flemish, and appeared under the title of ‘Kruydtbœck’ in 1581, dedicated to William of Orange, and the Burgomasters and other functionaries of Antwerp. The blocks (see Text-fig. 67) used to illustrate this work were taken from previous books, especially those of de l’Écluse. Immediately after the publication of the Kruydtbœck, Plantin brought out an album of the engravings it had contained, which, although they had been also used to illustrate the herbals of Dodoens and de l’Écluse, were now grouped according to de l’Obel’s arrangement, which was recognised as the best. 3. THE HERBAL IN ITALY. The Italian botanists of the Renaissance devoted themselves chiefly to interpreting the works of the classical writers on Natural History, and to the identification of the plants to which they referred. This came about quite naturally, from the fact that the Mediterranean flora, which they saw around them, was actually that with which the writers in question had been, in their day, familiar. The botanists of southern Europe were not compelled, as were those whose homes lay north of the Alps, to distort facts before they could make the plants of their native country fit into the procrustean bed of classical descriptions. One of the chief of the commentators and herbalists of this period was Pierandrea Mattioli [or Matthiolus] (Text-fig. 40), who was born at Siena in 1501, and died of the plague in 1577. We realise something of the frightful extent of this scourge, when we remember that it claimed as victims no less than three of the small company of Renaissance botanists, Gesner, Mattioli and Zaluzian. Leonhard Fuchs was brought into fame by his successful treatment of one of these epidemics. It should also be recalled that, while Gaspard Bauhin, one of the best known of the later herbalists, was practising as a physician at Basle, no less than three of these terrible outbreaks occurred in the town. [Illustration: Text-fig. 40. Pierandrea Mattioli, 1501-1577 [Engraving by Philippe Galle. Virorum Doctorum Effigies, Antwerp, 1572].]