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WO names," says M. Leo Herrera, in the "Revue Scientifique," "are inseparably connected with that grand movement of the biological sciences that began about 1838, and of which we to-day contemplate the superb bloom—Schleiden and Schwann. The two laid the foundations of the cellular theory. Both exercised a powerful influence over their contemporaries; both rendered lasting services to science through their teaching, their pupils, their ideas, and even through their errors."

Schleiden devoted himself variously to law, medicine, the natural sciences, and philosophy, and his works bear the marks of those diversified studies: but he was, above all, a botanist; it was under this title that he became famous, and by this his name must endure.

was the son of the physicist, Andreas Benedict Schleiden, and was born in Hamburg, April 5, 1804. On quitting the gymnasium he entered upon the study of the law at Heidelberg in 1824. He received his degree in 1827, and had entered upon the practice of his profession in his native city, when, in 1831, he concluded that the natural sciences were more to his taste than the law. With the encouragement of his father, he returned to the university, and studied medicine at Göttingen—where he enjoyed the instructions of Bartling in botany—and the natural sciences at Berlin, where his uncle, the botanist Horkel, enlisted his special interest in that branch. In 1839 he was appointed, on the recommendation of Humboldt it is said, Adjunct Professor of Botany at Jena, where he continued to teach in the chair of that science till 1862.

Schleiden was thirty-three years old when he published his first works; the scientific collections from 1837 to 1852 contain twenty-seven memoirs contributed by him. The most striking of these essays and the ones which contributed most directly to his rapid rise to eminence, were those in which he propounded his theories of the origin of plant-cells and of fructification. These were the "Beitrage zu Phytogenesis" "Contributions to Phytogenesis," 1838), and "Ueber Bildung des Eichens und Entstehung des Embryos beim Phanerogamen" ("On Formation of the Ovule and Origin of the Embryo in Phanerogams," 1839)—his "most remarkable, most revolutionary, and most erroneous works," which astonished the world, "just as he had barely made himself known by a few anatomical and organo-genical researches." Both of these works called forth lively responses. They were translated into English and French. They were commented upon and discussed, and were the subject of passionate debates; in short, inquiry was awakened, and an impulse was given to investigation, the force of which has not slackened to this day.