It is well-known to historians of science that biological models were frequently applied to explanations of the physical and chemical behaviours of natural substances in early chemistry. Vegetable models of growth or maturation were the favourite of the medieval Latin alchemists. And late sixteenth-century mineral science in particular saw the diffusion of ideas of this kind. Among these, the Renaissance concept of “seed” seems to me the most striking one.
 
        The concept of seed, established under the authority of Plato during the late Renaissance by Neoplatonic thinkers, is the missing link that unites the medieval theory of the “substantial form” of the Scholastics and the theory of the “molecules” of the mechanistic philosophers of the seventeenth century. It was designed to explain the origin of the specificity and the organisation of individual natural things, living and non-living, and their physical and chemical behaviours. The invisible spiritual “seeds” are considered as the vehicles of the form, or quiddity, of each natural being, including the new diseases unknown to the Ancient authors.
 
        In the Renaissance period, Marsilio Ficino of the Platonic Academy of Florence first formulated a metaphysical system incorporating the idea of invisible spiritual seeds diffused throughout Nature. For this theory, he combined the Stoic theory of logoi spermatikoi, transmitted by such Neoplatonic thinkers as Plotinus and Proclus, with Lucretius’ atomistic idea of semina rerum. For Ficino, these seeds, which generate the forms of natural things in informed prime matter, are sent from the heaven by the spiritus mundi, the uniting bond of the World-Soul and its corporeal body (machina mundi). Agrippa of Nettesheim is one of the earliest followers of this Ficinian concept and the French physician Jean Fernel introduced it into the learned medical milieu through his very popular book On the Hidden Causes of Things (Paris, 1548). But Paracelsian chemical philosophers played a decisive role. For Paracelsus himself, every natural being is generated form its invisible seed, which contains its own three principles, Salt, Sulphur and Mercury. The seed of each natural being is the prime state of its development, “predestined” by God the Creator to arrive at its ultimate end for the use of man.
 
        Uniting this Paracelsian idea with that transmitted by Jean Fernel, the Danish Paracelsian Petrus Severinus established a landmark in the history of the concept of seed by his book, Idea medicinae (Basel, 1571). For Severinus, the seed of each natural thing (animal, plant, or mineral) is endowed with the predestined scientia, which contains all the information for its later development, as well as craftsman-like “mechanical spirits”, regulators of this development according to the scientia. Among the followers of Severinus, Joseph Duchesne stressed the chemical aspects of the  Severinian system while Oswald Croll developed its theological dimension. Following Duchesne, Anselmus Boetius de Boodt, the court mineralogist of the emperor Rudolf II, introduced these ideas into his theory of mineral formation in his popular mineralogical work. Because the concept of seed fit well with the traditional alchemical theory of “metallic seeds” and the famous “mineral physiology” of Girolamo Cardano, it became a standard mineralogical theory for serious thinkers in the first half of the seventeenth century.
 
        Under the manifest influence of the system of Severinus, the Flemish alchemist Van Helmont developed his ideas of “seminal principle” and “archeus faber”, forged on the model of Severinian “mechanical spirits”. The French atomist Pierre Gassendi, for his part, invented the term “molecule” and identified his molecules with “seeds” of things. For Gassendi, these seed-like molecules were directly created from atoms by God in the first days of the creation and are endowed with their own scientia for the further organisation of natural things. He clearly acknowledges his indebtedness to the Danish Paracelsian for this idea. Thus, these two giants of the scientific revolution, Van Helmont and Gassendi, shared a key source in constructing their theories of matter, totally divergent to our modern eyes. This fact helps us to understand why the most important seventeenth-century chemist, Robert Boyle, had no difficulty in integrating the Helmontian theory of “seminal principle” into his mechanical corpuscular philosophy of matter, which he inherited much from Gassendi.
 
        The trajectory of the Renaissance concept of seed provides us a fascinating example of the application of biological models to early modern matter theories.