Theophrastus, the Father of Botany

When Aristotle quit Athens for the last time, he left his friend and assistant Theophrastus (ca. 372–ca. 287 b.c.e.) to lead the Peripatetic school. In his will Aristotle bequeathed the Lyceum buildings and garden and his library to Theophrastus and made Theophrastus guardian of his children. Theophrastus was a popular teacher, some accounts claiming he had 2,000 students, and he lived to a good age. His dying words are alleged to have been a complaint that he was just beginning to gain an insight into life's problems.

Theophrastus was not his real name. He was born as Tyrtamus, and Theophrastus, which means “divine speech,” was a nickname, probably given to him by Aristotle and referring to his skills with the spoken word. All that is known about the life of Theophrastus comes from Lives and Opinions of Eminent Philosophers, a book by Diogenes Laertius, who lived about 400 years later and about whom even less is known, not even the years he was born and died. According to Diogenes Laertius, Theophrastus wrote 227 major works as well as a number of shorter ones. Most of these have survived only as titles or fragments, and they consist of what appear to be lecture notes rather than the texts of books. The two exceptions are Theophrastus's most important works: De historia plantarum (On the history of plants) and De causis plantarum (On the reasons for plant growth). With these works Theophrastus initiated the methodical study of plants.

Theophrastus grew plants in his own botanical garden and he encouraged his students, many of whom lived a long way from Athens, to observe the plants that grew near their homes. Theophrastus described more than 500 plant species and varieties, classifying them as trees, shrubs, undershrubs, and herbs. He was the first person to distinguish between monocotyledons and dicotyledons.

Monocotyledons produce a single seed leaf (cotyledon) and the leaves have parallel veins (grasses are typical); dicotyledons produce two or more cotyledons and the leaves have a network of veins (cabbages are typical). He recognized a fundamental difference between trees that produce cones, such as pines and firs, and those that bear true flowers, such as oaks and aspens. He recorded the different ways plants can reproduce—from seed, cuttings, or roots—and noted that when cultivated trees were grown from seed they often reverted to the wild type, but wild trees did not change from one generation to the next. He described seed germination and the anatomy of different types of flowers, noting that some flowers have petals and others have none.

Not surprisingly, for centuries De historia plantarum and De causis plantarum were the basic texts for teaching botany. They were translated into Latin in 1483 and again in 1497 and a German translation appeared in 1822. Theophrastus's reports were usually accurate, although he relied for his information about African and Asian plants on accounts by individuals who had taken part in the campaigns of Alexander the Great.

De historia plantarum consisted of nine volumes. Volume 1 described plant anatomy. Volumes 2 through 5 were on woody plants, including instructions on cultivation, the treatment of diseases, and the uses and treatment of wood. Volume 6 described herbaceous perennials, volume 7 vegetables and their cultivation, volume 8 cereals, peas, and beans, and volume 9 saps and medicines derived from plants. De causis plantarum consisted of six volumes. Volume 1 was on plant reproduction and growth, volume 2 on the environmental factors that affect plants, volume 3 on plant cultivation, volume 4 on the origin and propagation of cereals, volume 5 on plant diseases, and volume 6 on plant flavors and odors. Theophrastus richly deserved the title of father of botany.

Theophrastus was born in about 371 at Eresus (modern Eressos) on the Greek island of Lesbos. He commenced his education on Lesbos, where his teacher Leucippus (or Alcippus) introduced him to the philosophy of Plato. Theophrastus enrolled at Plato's Academy in Athens, and when Plato died he became a follower of Aristotle, probably remaining with him during the time Aristotle spent in Macedon. By all accounts Theophrastus was a kind, generous man and highly popular. When an attempt was made to bring a charge of impiety against him, the case collapsed. After his death in about 287 b.c.e. Theophrastus was given a public funeral, and Diogenes Laertius wrote that the entire population of Athens turned out to honor him.