The theoretical introduction to his excellent and copious remarks on the parts of fructification may supply another example of Cesalpino’s peripatetic method: ‘As the final cause (‘finis’) of plants consists in that propagation which is effected by the seed, while propagation from a shoot is of a more imperfect nature, in so far as plants do exist in a divided state, so the beauty of plants is best shown in the production of seed; for in the number of the parts, and the forms and varieties of the seed-vessels, the fructification shows a much greater amount of adornment than the unfolding of a shoot; this wonderful beauty proves the delight (‘delitias’) of generating nature in the bringing forth of seeds. Consequently as in animals the seed is an excretion of the most highly refined food-substance in the heart, by the vital warmth and spirit of which it is made fruitful, so also in plants it is necessary that the substance of the seeds should be secreted from the part in which the principle of the natural heat lies, and this part is the pith. For this reason, therefore, the pith of the seed (that is, the substance of the cotyledons and of the endosperm) springs from the moister and purer part of the food, while the husk which surrounds the seed for protection springs from the coarser part. It was unnecessary to separate a special fertilising substance from the rest of the matter in plants, as it is separated in animals which are thus distinguished as male and female.‘ This last remark and some lengthy deductions which follow are intended to prove, after the example of Aristotle, the absence and indeed the impossibility of sexuality in plants, and accordingly Cesalpino goes on to compare the parts of the flower, which he knew better than his contemporaries, with the envelopes of the ova in the foetus of animals, which he regards as organs of protection. Calyx, corolla, stamens, and carpels are in his view only protecting envelopes of the young seed, as the leaves are only a means of protecting the young shoots. Moreover by the word flower (‘flos’) Cesalpino understands only those parts of the flower which do not directly belong to the rudiment of the fruit, namely, the calyx, the corolla, and the stamens. This must be borne in mind if we would understand his theory of fructification, and especially his doctrine of metamorphosis. We must also note, that by the expression pericarp he understands exclusively juicy edible fruit-envelopes, though at the same time pulpy seed-envelopes inside the fruit pass with him for pericarps. The parts of his flower are the ‘folium,’ which evidently means the corolla, but in certain cases includes also the calyx; the ‘stamen,’ which is our style; and the ‘flocci,’ our stamens. We see that Cesalpino uses the same word ‘folium’ without distinction for calyx, corolla, and ordinary leaves; just as he, and Malpighi a hundred years later, unhesitatingly regarded the cotyledons as metamorphosed leaves.