Botanical investigations

Of all the works of Aristotle that have survived, none deals with what was later differentiated as botany, although it is believed that he wrote at least two treatises on plants. Fortunately, however, the work of Theophrastus, one of Aristotle’s students, has been preserved to represent plant science of the Greek period. Like Aristotle, Theophrastus was a keen observer, although his works do not express the depth of original thought exemplified by his teacher. In his great work, De historia et causis plantarum (The Calendar of Flora, 1761), in which the morphology, natural history, and therapeutic use of plants are described, Theophrastus distinguished between the external parts, which he called organs, and the internal parts, which he called tissues. This was an important achievement because Greek scientists of that period had no established scientific terminology for specific structures. For that reason, both Aristotle and Theophrastus were obliged to write very long descriptions of structures that can be described rapidly and simply today. Because of that difficulty, Theophrastus sought to develop a scientific nomenclature by giving special meaning to words that were then in more or less current use; for example, karpos for fruit and perikarpion for seed vessel.More From Britannicahistory of science: The founding of modern biology

Although he did not propose an overall classification system for plants, more than 500 of which are mentioned in his writings, Theophrastus did unite many species into what are now considered genera. In addition to writing the earliest detailed description of how to pollinate the date palm by hand and the first unambiguous account of sexual reproduction in flowering plants, he also recorded observations on seed germination and development.