Hedwig, Johann
Hedwig, Johann
(b. Kronstadt [now Braşov], Transylvania [now Rumania], 8/10 December 1730; d. Leipzig, Germany, 7 February 1799)
botany.
Hedwig’s father, Jakob Hedwig, a town councillor, was probably a wine merchant by trade; his mother was Agnes Galles. He attended schools in his native town, in Pressburg (now Bratislava, Czechoslovakia), and Zittau, Germany. In 1752 he entered the University of Leipzig, receiving the bachelor’s degree in 1756 and the M.D. in 1759. His studies included philosophy and mathematics as well as the medical sciences; and among his teachers, who were impressed with his character and abilities, were the eminent botanists J. E. Hebenstreit, C. G. Ludwig, and G. R. Böhmer. The professor of botany, E. G. Bose, invited Hedwig to lodge in his home and employed him for three years as his assistant at the hospital; without this help he might have been unable to complete his studies, for since his father’s death in 1747 his family could no longer afford to pay all his expenses.
After graduation Hedwig wished to practice medicine in Kronstadt but was disappointed to find that a medical degree from the University of Vienna was required. On the advice of a friend in Chemnitz, Saxony, he decided to settle in that town, shortly afterward marrying Sophie Teller, daughter of Romanus Teller, professor of theology and minister of the Thomaskirche in Leipzig.
Although a busy and successful medical practitioner, Hedwig gave much time to the study of plants, in which he had been passionately interested since childhood. He began work at dawn and often spent several hours botanizing in the country before visiting his patients, examining his collections at the end of the day. He became increasingly occupied with the mosses and liverworts, but a shortage of books and equipment due to lack of money were at first a handicap: his only book on the lower plants was a “meagre excerpt” from J. J. Dillenius’ Historia muscorum (1741). J. C. D. Schreber, who himself made important contributions to the knowledge of mosses, later encouraged him and provided him with books, and J. G. Köhler, inspector of mathematical instruments at Dresden, gave Hedwig an excellent compound microscope made by Rheinthaler of Leipzig. The death of his wife in 1776 and the problems of caring for his six surviving children interrupted Hedwig’s botanical work for a while, but in 1778 he was persuaded by his friends to marry again, and his second wife, Clara Benedicta Sulzberger of Leipzig, worked actively to promote his scientific career as well as his personal welfare. She bore him six more children, of whom five died in early childhood and one at the age of sixteen.
In 1781, at his wife’s suggestion, and in the interests of his botanical work and his children’s education, Hedwig moved to Leipzig. There he continued to practice medicine and the following year published his Fundamentum historiae naturalis muscorum frondosorum, the first of his works to attract wide attention in Germany and abroad.
Having thus achieved international recognition after years of poverty and neglect. Hedwig’s abilities now began to receive their due. In 1784 he was given charge of the military hospital at Leipzig, and in 1791 he became medical officer of the Thomasschule. In 1786 the university made him extraordinary professor of botany, and in 1789 he succeeded J. E. Pohl as ordinary professor, a post which carried with it the directorship of the botanical garden and an apartment in the Academy building. Because he did not hold the M.A. degree Hedwig was ineligible for a chair under the university regulations and was appointed only after the intervention of Friedrich August I, elector of Saxony, himself a keen botanist, who urged that a rule intended to exclude unsuitable candidates should not be used to debar a man of recognized merit.
Hedwig’s fame spread widely in his own country and abroad. In 1783 he won a prize offered by the Russian Academy of Sciences for work on the reproduction of cryptogamic plants; his thesis was published the following year in St. Petersburg under the title Theoria generationis et fructificationis plantarum cryptogamicarum Linnaei. He was elected to membership in several German and foreign academies and scientific societies, including the Royal Society of London, of which he became a fellow “on the foreign list” in 1788. On 8 January 1797 Goethe visited Hedwig, who showed him “beautiful preparations and drawings.”
During the exceptionally cold winter of 1798–1799 Hedwig continued to visit his patients as usual, without taking adequate care of his own health. Having barely recovered from a “catarrhal fever,” he contracted a “nervous fever” of which he died nine days later.
Among Hedwig’s several important contributions to science, the best known and probably most significant was the better understanding of the life history and reproduction of the lower plants resulting from his observations on mosses. At the time this work was being done, very little was known about the sexual reproduction of the lower plants, hence Linnaeus’ name for them, Cryptogamia (“plants of the hidden marriage”). Erroneous ideas were current, mainly owing to misguided attempts to interpret the functions of the reproductive organs of ferns and mosses by reference to the relatively well-understood reproductive parts of flowers. Thus Linnaeus and most of Hedwig’s contemporaries believed that because of their similarities to the pollen of the higher plants, the spores of mosses functioned as male organs and that the spore capsule (sporogonium) was there-fore the equivalent of the anther.
Hedwig, in a preliminary paper, “Vorläufige Anzeige seiner Beobachtungen von den wahren Geschlechtstheilen der Moose” (1779), showed that the much smaller and less conspicuous antheridia (which he termed anthers) were the true male organs and that the minute cells emitted from them are the male gametes and fertilize the archegonia (pistilla of Hedwig). He also observed the germination of the spores and the growth from them of the filamentous protonema (cotyledons of Hedwig), which is the juvenile form of the moss “plant” or gametophyte. The views which he had already formed on the true functions of the antheridia were finally confirmed by his observation, on 17 January 1774, of “Kügelchen” (minute particles, that is, sperm cells) being discharged from the antheridia of the moss Grimmia pulvinata. Some years earlier a similar observation had been made on the liverwort Fossombronia by C. C. Schmidel, who also realized that the antheridia were the male organs but did not pursue his observations with the same thoroughness as Hedwig.
The observations of Schmidel and Hedwig did much more than merely demonstrate the true functions of the antheridia and spores in bryophytes: they were crucial in preparing the way for the fundamental work of Wilhelm Hofmeister, who eventually elucidated the life histories of the higher cryptogams and demonstrated the true homologies between their reproductive organs and those of flowering plants.
Unfortunately, Hedwig’s studies of ferns were less successful than his work on mosses. He mistook the glandular hairs on the leaves of certain ferns for antheridia, not having understood the importance of the prothalli (gametophytes) which bear the true antheridia. It was left to Karl von Naegeli to discover the antheridia and sperm cells of ferns in 1844.
Hedwig’s views on the sexuality of mosses did not receive immediate or unanimous acceptance: for some years after they were published, some of his contemporaries were maintaining that the mosses were “viviparous,” or that they had no form of sexual reproduction; even in 1806 Ambroise Palisot de Beauvois put forward views completely at variance with the observations of Schmidel and Hedwig.
Among Hedwig’s other contributions on the lower plants were his clear distinction between mosses and liverworts and his demonstration of the value, in the classification of mosses, of the peristome, the minute, elaborately constructed teeth which surround the mouth of the spore capsule. His classification of mosses, largely based on peristome characters, is embodied in his Species muscorum frondosorum (1801), in which all the then known species of mosses are described. This work, now used as the basis of the modern scientific nomenclature of mosses, was edited and published after Hedwig’s death by C. F. Schwaegrichen, who later added several supplements.
Hedwig worked on fungi and other lower plants as well as mosses and wrote extensively about the microscopic structure of higher plants, although he frequently misinterpreted his observations and contributed little of permanent value in this field. He was the first to describe the stomata of flowering plants (although Marcello Malpighi and others had previously seen them in ferns). He observed their opening and closing and had a fair understanding of their function.
His interests were not limited to academic science. Hedwig wrote also on practical subjects, such as the liver fluke disease of sheep and the value of false acacia (Robinia) timber as firewood; he even wrote a reply to the inquiries of the English agricultural reformer Arthur Young on the irrigation of meadows with spring water and the cause of mildew in wheat.
Distinguished above all for exact and patiently repeated observations, Hedwig’s work depended on the skillful use of dissection and the compound microscope. At first he used a simple lens magnifying 6X, but by successive improvements to the compound microscope given to him by Koehler he was eventually able to use magnifications of up to 290X. In his Fundamentum (ch. 2, pp. 9–11) he explains his method of dissecting mosses with the aid of needles and small knives, mounting the preparations in drops of water on glass slides—essentially the technique used today. He recorded his observations in accurate drawings. Although he did not teach himself to draw until the age of forty, the figures in his Descriptio (1787–1797) are among the most accurate and beautiful illustrations of mosses of his own or any other period.
Hedwig was a good teacher, and his character endeared him to his family, friends, and students. On the field excursions which he organized for his students he is said to have been indefatigable, but nevertheless the excursions were regarded as a pleasure rather than as an imposed task.
Hedwig’s attitude toward his botanical work is indicated by the mottos with which he prefaced his works. The Fundamentum has a line from Cicero (inaccurately quoted): “Opinionis commenta delet dies, naturae iudicia confirmat” (“The passage of time obliterates the fabrications of opinion, but confirms the judgments of nature”). The motto of the Descriptio is a quotation from Dillenius which indicates that, like most of his predecessors, Hedwig believed that the aim of botanical research such as his own was to understand better the wisdom of the Creator.
BIBLIOGRAPHY
I. Original Works. A complete list of Hedwig’s writings (32 items) by C. F. Schwaegrichen forms an app. to Hedwig’s posthumous Species muscorum frondosorum, pp. 318–327. His major works are “Vorläufige Anzeige seiner Beobachtungen von den wahren Geschlechtstheilen der Moose und ihrer Fortpflanzung durch Saamen,” in Sammlungen zur Physik und Naturgeschichte von einigen Liebhabern dieser Wissenschaften, 1 (1779), 259–281; Fundamentum historiae naturalis muscorum frondosorum, 2 vols. (Leipzig, 1782); Theoria generationis et fructificationis plantarum cryptogamicarum Linnaei (St. Petersburg, 1784); Descriptio et adumbratio microscopico-analytica muscorum frondosorum nec non aliorum vegetantium e classe cryptogamica Linnaei, 4 vols. (Leipzig, 1787–1797), sometimes called Stirpes cryptogamicae novae; Theoria generationis et fructificationis plantarum cryptogamicarum Linnaei, rev. and enl. ed. (Leipzig, 1798); and Species muscorum frondosorum, C. F. Schwaegrichen, ed. (Leipzig, 1801), repr. in the series Historiae naturalis Classica, J. Cramer and H. K. Swann, eds., with intro. by P. A. Florschütz (Weinheim–Codicote, Hertfordshire–New York, 1960).
II. Secondary Literature. See J. P. F. Deleuze, “Notice sur la vie et les ouvrages d’Hedwig,” in Annales du Muséum national d’histoire naturelle, 2 (1803). 392–408, 451–473; H. Dolezal, “Hedwig, Johann, Botaniker,” in Neue deutsche Biographie, VIII (1969), 191–192, which gives further references; P. A. Florschütz. intro. to repr. of Hedwig’s Species muscorum frondosorum (see above); I. Györffy, “Zum Andenken an Joannes Hedwig am zweihundertsten Jahreswechsel seiner Geburt,” in Revue bryologique et lichénologique, n.s. 57 (1930). 161-165, which has a photograph of the parish register with the entry for Hedwig’s baptism; W. D. Margadant, “Early Bryological Literature,” doctoral thesis Univ. of Utrecht (Hunt Botanical Library, Pittsburgh, Pa., 1968), see pp. 139–144 for biography and bibliographical account of Hedwig’s Species muscorum frondosorum; J. Römer, “Aus dem Leben eines Microskopikers der Linneschen Zeit. Eine historische Studie,” in Mikrokosmos, 2 (1908–1909), 91–97; and C. F. Schwaegrichen, “Hedwigii vita,” app. to Hedwig’s Species muscorum frondosorum (see above).
P. W. Richards
Büring, Johann Gottfried
Bibliography
W&M (1987)
Boumann, Johann A.
Bibliography
W&M (1987)