Marcello Malpighi and the Microscopic Study of Plants

Nehemiah Grew moved from Coventry to London partly to gain access to the microscopes owned by the Royal Society. Scientists recognized the value of these instruments, and Grew made extensive use of them. It was the Italian physician Marcello Malpighi (1628–94), however, who really pioneered the use of the microscope in the study of anatomy. Malpighi became best known for his microscopic studies of animals, but he also studied plants. In 1671 he published a two-volume work Anatomia plantarum (Plant anatomy). The Royal Society published the two volumes in London in 1675 and 1679.

Malpighi had first been intrigued by what looked like fine threads emerging from the branch of a chestnut tree where the branch had been broken. He had earlier discovered the fine tubes, called trachaea, passing through the external skeleton through which air enters the body of an insect, and he assumed these served a similar function in plants. He found that the plant structures were long tubes, thickened at intervals. His observation was accurate, but his interpretation was mistaken. In fact he was looking at xylem—the vessels, made from elongated cells joined end to end, along which water is transported from the roots to every part of the plant.

His enthusiasm aroused, Malpighi watched and drew the stages in the germination of seeds. He was the first scientist to describe the nodules on the roots of leguminous plants, though he was unaware that these were colonies of bacteria that converted atmospheric nitrogen into compounds the plant absorbed in return for carbohydrates the bacteria absorbed from the plant. He studied plant galls and found that some of them contained an insect larva.

Marcello Malpighi was born on his family's farm at Crevalcore, not far from Bologna, Italy, on March 10, 1628. When he was 17, he enrolled at the University of Bologna to study philosophy, but had to interrupt his education for more than two years following the deaths of both his parents and his grandmother. He returned to the university and in 1649 began to study medicine. He graduated in philosophy, qualified as a physician in 1653, and applied unsuccessfully for a post as a lecturer. His application succeeded in 1655, but after a few months he became professor of theoretical medicine at the University of Pisa. Illness forced Malpighi to leave Pisa in 1660, and he returned to Bologna, but left again in 1662 to become the first professor of medicine at the University of Messina for a four-year period, after which he went back to Bologna as professor of medicine, where this time he remained for 25 years. In 1691 he moved to Rome to become private physician to Pope Innocent XII. He died in Rome from apoplexy on November 30, 1694.