fruticans_ L., and species of _Thalictrum_, are included among the trifoliate forms, and _Dictamnus Fraxinella_ among the "Leguminosa." The _Stirpium Historiae Pemptades Sex sive Libri XXX_ of Dodoens, published in 1583, shows considerable progress in classification as compared with his _Cruydtboeck_ of 1554, more particularly in the recognition, apparently for the first time, of umbelliferous plants as a distinct group in a chapter headed _De Umbelliferis Herbis_. Possibly these attempts to introduce some sort of system into Botany may have been inspired by the teachings of Conrad Gesner, that universal genius, who lived about this time (1516-1565). Though but fragments of his botanical writings have survived, it is clear from the much-quoted passage in a letter of his dated Nov. 26, 1565 (_Epistolae Medicae_, 1577, p. 113) that he too was seeking for the basis of a natural system of classification and that he thought he had found it in the flower and the fruit:--"_Ex his enim notis_ (_a fructu_, _semine_ and _flore_) _potius quam foliis, stirpium naturae et cognationes apparent_." Evidently at this period classification was in the air, and at length it began to precipitate and to crystallise in the work of Andrea Cesalpino (Caesalpinus: 1519-1603), Professor in the University of Pisa, whose _De Plantis Libri XVI_, published in 1583, is one of the most important landmarks in the history of systematic Botany. Here for the first time a system is propounded which is based definitely upon morphological observation. Cesalpino turns to the "fructification," that is the flower and the fruit, for his distinguishing characters. "_Enitamur igitur_," he says (Lib. I. _cap._ xiv.), "_ex propriis quae fructificationis gratia data sunt, plantarum genera investigare_"; and he goes on to point out that the observable differences here depend on number, position and form of the parts:--"_ad organorum constitutionem tria maxime faciant, scilicet, partium numerus, situs et figura_." These principles he illustrates as follows:--the flower being the outermost covering of the fruit, a single flower may cover a single seed, as in the Almond: or a single seed-receptacle as in the Rose: or two seeds, as in the Umbelliferae: or two seed-receptacles, as in the Cress: or three seeds, as in the genus _Tithymalus_ (_Euphorbia_); or three receptacles, as in the Bulbaceous plants (petaloid Monocotyledons): or four seeds, as in _Marrubium_: or four receptacles, as in _Euonymus_: or many seeds, as in the Cichoriaceae: or many receptacles, as in the Coniferae. The feature of the relative position of the parts which he especially emphasizes is whether the flower is inserted upon the top of the fruit (_i.e._ is epigynous): or is inserted lower around the fruit (hypogynous or perigynous). Moreover, the form of the seed, of the seed-receptacle, and of the flower, is to be taken into account.