Strasburger, Eduard Adolf
STRASBURGER, EDUARD ADOLF
(b. Warsaw, Poland, 1 February 1844; d. Poppelsdorf, Germany, 19 May 1912)
botany, plant cytology.
Strasburger, who clarified the phenomena of cell division and the role of the nucleus and chromosomes in heredity, was born in Warsaw, when the city was under Russian rule. He was the eldest son of Eduard Gottlieb Strasburger, a merchant, and Anna Karoline von Schütz. Both parents were of German descent. He received his early schooling in Warsaw and, upon completing his Gymnasium studies, went to Paris in 1862 and studied for two years at the Sorbonne. He continued in botany under Hermann Schacht at the University of Bonn and gained the technical skill in microscopy that proved invaluable to him. Julius von Sachs lectured at the Agricultural Academy at Poppelsdorf, a suburb of Bonn, providing further stimulus to Strasburger’s botanical interests. Strasburger met Nathanael Pringsheim when the latter visited Bonn. Upon the unexpected death of Schacht, Strasburger decided to go to Jena and accept an offer to become an assistant in Pringsheim’s laboratory.
Pringsheim in time became his friend as well as his teacher, and Strasburger valued his critical mind; but his imagination was taken by the more speculative approach of the professor of zoology, Ernst Haeckel, especially by Haeckel’s enthusiasm for Darwin’s theory of evolution. Haeckel’s lecturers and their long discussions on development determined the direction of Strasburger’s work, and he always recalled the influence of Darwin’s Origin of Species. Thereafter Strasburger was an evolutionist and applied phylogenetic interpretations to the structure and developmental history of plants.
As Pringsheim’s student, Strasburger also studied chemistry and zoology. He received the doctorate at Jena in 1866 with the thesis “Asplenium bulbiferum, ein Beitrag zur Entwicklungsgeschichte des Farnblattes mit besonderer Berücksichtigung der Spaltöffnungen und des Chlorophylls.” The dissertation was not published, but his results appeared that year in an article in Pringsheim’s Jahrbuch für wissenschaftliche Botanik and were used when he habilitated in 1867 at the University of Warsaw as Privatdozent.
Through the offices of Haeckel, Strasburger was appointed professor extraordinarius at Jena following Pringsheim’s retirement and was made director of the botanical gardens; he became full professor two years later, at twenty-seven. In 1870 he married Alexandrine Wertheim, from Warsaw; they had a daughter and a son, Julius, later professor of medicine at Breslau. Strasburger accompanied Haeckel on a scientific trip to Egypt and the Red Sea in 1873, and it was Haeckel who first described to Strasburger the beauties of the Italian Riviera, where he later vacationed. Always interested in the plants of the regions he visited, Strasburger wrote popular articles and a book, Streifzüge an der Riviera (Berlin, 1895, Jena, 1904), which was later translated as Rambles on the Riviera (London, 1906).
During his twelve years at Jena. Strasburger published his botanical investigations. The development of his cytological observations can be followed in the three editions of his Zellbildung und Zelltheilung (1875, 1876, 1880).
Strasburger succeeded Johannes von Hanstein at the University of Bonn as ordinary professor, and in 1881 he transferred to Bonn his morphological and physiological work and investigations of plant reproduction and cytology. He spent the rest of his career there, and his laboratory became the leading center for the study of plant cytology.
Strasburger noted the appearance of plant cells even in his early research, reporting in his doctoral thesis that in the cells of a fern he had seen the nucleus divide during cell division. At that time the nucleus of the dividing cell was generally thought to disappear. The year he came to Jena he published a book on fertilization in conifers, but although his investigations followed upon Wilhelm Hofmeister’s work on the alternation of generations, Strasburger wrote, “I was never closely associated with Hofmeister. Unfortunately, during the latter part of his life, Hofmeister became very sensitive and was angry because in 1869 in my work on Befruchtung bei den Coniferen I sought to prove that the ‘corpuscula’ do not correspond to the embryo sacs of angiosperms, but are archegonia” (Chamberlain, Botanical Gazette, 54 , 70).
In Die Coniferen und die Gnetaceen (1872), Strasburger discussed the morphology of the flower and the origin of tissues. While zoologists independently observed and described the stages of cell division in 1873, using animal cells that were especially suitable because of their transparency, Strasburger, studying the embryogeny of the Coniferae, noticed and followed the formation of the nuclear spindle. He pioneered methods of fixing and hardening tissues, using pure alcohol. His observations on the phenomena of plant cells were included in his Zellbildung und Zelltheilung, (1875 – 1880), and in such papers as “Über Befruchtung und Zelltheilung” (1877) and “Über Polyembryonie” (1878).
The embryo sacs of certain plants permitted numerous nuclei to be seen at the same time in different phases of division. In his illustrations and descriptions, he noted the formation of the equatorial plate, the longitudinal extension of rods that met at the two poles, and the succession of events that paralleled the phenomena being reported by his colleagues in the division of animal cells. This suggested to Strasburger the common descent of vegetable and animal cells, which Haeckel had maintained. As he examined Spirogyra and other simple forms, he was again impressed by the difficulties in differentiating the plant from the animal kingdom. He was also carrying on physiological experiments, studying the reactions of swarm spores when he changed the conditions of light and temperature. Strasburger originated a number of terms in the course of his work, among them “phototaxis” and “chloroplast” and later, “cytoplasm,” “nucleoplasm,” “haploid,” and “diploid.” He saw the relation between his physiological and morphological investigations. He no doubt had his swarm spore researches in mind when in 1894 he reported that he had unsuccessfully tried to arrest the division of nuclei by lowering the temperature or varying the light. He felt that they might thus be more conveniently observed, especially in multinucleate forms, than when the successive stages of division occurred at chance times.
In 1875 Strasburger thought that free cell formation took place; in the 1880 edition of Zellbildung und Zelltheilung he no longer held this view. Meanwhile, in the 1870’s there had been a continuing series of observations: Oscar Hertwig in 1875 had seen the spermatozoon as it entered the ovum and inferred that the fusion of the nuclei was the aim of fertilization; and Walther Flemming, aided by stains that distinguished the fibrils within the nucleus, had described in 1879 the nuclear threads with illustrations, and had clearly shown that these chromatin-staining bodies split longitudinally during division. In 1880 Strasburger still maintained that there was a transverse division of the bodies within the nucleus (first to be called chromosomes by Wilhelm Waldeyer in 1888), but as he often did when the evidence required, he changed his interpretation. Wilhelm Pfitzner in 1882 showed in detail the longitudinal segmentation, and the next year Wilhelm Roux pointed out the implications of the process–then called indirect division–for heredity.
In 1884, from his observations of plants, Strasburger independently concluded, as did Hertwig, August Weismann, and Albert von Koelliker at about the same time, that the nucleus was responsible for heredity, and that it contained within the filaments the substance that was divided in halves between the daughter cells and bore the characters of the parents and earlier ancestors.
For Strasburger the fertilization processes of the phanerogams demonstrated the role of the nucleus of the spermatozoon. He considered the male and female germ cells to be equivalent and the bearers of heredity. He now maintained that the longitudinal splitting assured the proportionate distribution of the substances in the nuclear threads, setting forth his views in “Die Controversen der Indirecten Kerntheilung” and Neue Untersuchungen über den Befruchtungsvorgang bei den Phanerogamen als Grundlage für eine Theorie der Zeugung (Jena, 1884). Strasburger gathered observations from his own and other researches to show that “fertilization depends only on the cell nuclei,” He believed that there was a reciprocal dynamic action between the cell nucleus and the surrounding cytoplasm, but although both exerted influence, the nucleus in a way governed the cytoplasm and controlled metabolism and growth, among other process.
Straburger studied the formation of the cell plate in plant material and the growth of the cell wall, which he considered to occur through apposition. Throughout his life he continued his cytological researches; he was interested in the role of the centrosome and the problem of protoplasmic connections between cells; and he porposed (1892) that protoplasm was composed of structurally different substances, a more active kinoplasm in the fibrils and other structures, and trophoplasm, which was more concerned with nutrition.
Straburger investigated reproduction in plants from algae and mosses to cryptogams and phanerogams, and from an evolutionary standpoint viewed asexually reproducing organisms as the earlier forms from which sexually differentiated organisms descended (although some forms again lost this differentiation). He presented his ideas in his article “Ueber periodische Reduktion der Chromosomenzahl im Entwicklungsgang der Organismen” (Biologische Centralblatt, 14 ). From the life histories of plant forms, and from the simpler to more complex sequences in which sexual or asexual generations developed, Strasburger inferred the courses through which the plants must have evolved. He pointed out the advantages of asexual reproduction under favorable external conditions for the rapid increase of individuals of the species, while sexual reproduction provided for the species to meet unfavorable conditions, and he interpreted the significance of the alternation of generations as it appeared in the higher plants.
Strasburger investigated the anatomy, life history, and aspects of physiology of plants. References to his extensive and careful work can be found throughout the botanical literature of his day and afterward. His textbooks appeared in many editions and translations, and have been revised in recent years. He also carried on investigations of the movement of sap, and in 1891 he studied the movement of sap in trees and the forces propelling it.
Strasburger’s famous laboratory at the Botanical Institute of the University of Bonn was housed in the former palace of the electors of Cologne, in Poppelsdorf. The Institute also provided a residence for the professor of botany, with a laboratory and library. Strasburger directed the botanical gardens, which included outdoor collections, arboretums, and greenhouses, and sections containing special displays in which plants were grouped with reference to the solution of certain biological problems.
Under Strasburger, Bonn was foremost in plant cytology. Students came to his laboratory from all over Europe and as far away as Japan; but over half of the foreign students were American, in whom Strasburger took a special interest. They included Douglas H. Campbell, Charles J. Chamberlain, and B. M. Duggan. Bent from long hours spent over the microscope, Strasburger was an impressive teacher who gave each student his careful attention, yet steadily continued his own research. His clear and thoughtful lectures, his comprehensive views both of the broad principles and the fine details of morphology, his active involvement in the problems of the day, and his grasp of plant physiology exerted a lasting influence on the younger botanists. In addition, the laboratory and his textbooks provided methods and techniques essential to accurate experiment and observation. His texts included Das botanische Practicum, first published in 1884, and his renowned Lehrbuch der Botanik für Hochsulen, written with F. Noll, H. Schenck, and Andreas Schimper (Jena, 1894, and subsequent editions).
Strasburger had many interests beyond the Botanical Institute. He was rector of the University of Bonn in 1891–1892 (his inaugural address was entitled “Das Protoplasma und die Reizbarkeit”). Pringsheim died in 1894, and Strasburger became coeditor with Wilhelm Pfeffer of the Jahrbucher für wissenschaftliche Botanik. He belonged to the German Botanical Society, the Prussian Academy of Sciences, and many other scientific societies in Germany. He was a foreign member of the Royal Society of London, the Linnean Society, the American Academy of Arts and Sciences, and learned societies in Itlay, France, Belgium, and Ireland.
The goverment honored Strasburger with the title of Geheimer Regierungsrat in 1887, and he received honorary degrees in medicine from the University of Göttingen (1887) and in law from the University of Oxford (1894). The Linnean Society of London awarded Strasburger a medal in 1905 for his contributions to botanical histology and morphology and another medal three years later at the Darwin-Wallance celebration, in recognition of his contribution to the study of evolution. Strasburger was still teaching and engaged in research, with especial interest in questions of sex determination, when he died in 1912. He had been active in research and teaching for nearly fifty years and had linked his extensive botanical and cytological observations to the solution of central problems of heredity and evolution.
I. Original Works. For a retrospective view of Strasburger’s thought on the cell, see “The Minute Structure of Cells in Relation to Heredity,” in Darwin and Modern Science, A. C. Seward, ed. (Cambridge, 1909), 102–11. Strasburger’s many publications are listed by Beauverie, Tischler, and Küster, and by Clemens Müller (appended to Karsten’s obituary in the Berichte der Deutschen botanischen Gesellschaft, 80–86), in the articles cited below.
For Strasburger’s address upon accepting the Darwin-Wallace medal in 1908, see The Darwin-Wallace Celebration Held on Thursday, 1st July, 1908, by the Linnean Society of London (London, 1908), 22–24. A letter to Haeckel, recalling his debt to his teacher upon Haeckel’s sixtieth birthday, is found in Uschmann (see below), pp. 67–68. Strasburger’s autobiographical letter (Chamberlain, p. 70, see below) recounts his differences with Hofmeister and is a short but interesting personal account.
II. Secondary Literature. For discussions of Strasburger and his work, see J. Beauverie, “Édourd Strasburger,” in Revue généale de botaique, 24 (1912), 417–452, 479–479; Charles Chamberlain, “Eduard Strasburger,” in Botanical Gazette, 54 (1912), 68–72; Bradley M. Davis, “Eduard Strasburger,” in Genetics, 36 (1951), 1–3; L. F., “Professor Dr. Eduard Strasburger,” in Lotos, 60 (1912), 170–171; and J. B. F. “Prof. Eduard Strasburger,” in Nature, 80 (1912), 379–380.
For a student’s description of Strasburger as a teacher and of the laboratory at Bonn, see James Ellis Humphrey, “Eduard Strasburger,” in Botanical Gazette, 19 (1894), 401–405. Other accounts of Strasburger, his life and work, are B. D. J., “Eduard Strasburger,” in Proceedings of the Linnean Society of London (1911–19120, 64–66; G. Karsten, “Eduard Strasburger,” in Berichte der Deutschen botanischen Gesellschaft, 30 (1912), 61–80; and “Eduard Strasburger,” in Biographisches Jahrbuch und Deutscher Nekrolog, XVII (Berlin, 1915), 25–39; Ernst Küster, “Eduard STrasburger,” in Muenchener medizinsche Wochenschrift, 59 (1912), 1445–1447; and obituary in Sitzungsberichte der Niederrheinischen Gesellschaft für Natur- und Heillkunde zu Bonn (1912), 5–18. See also W. J. V. Osterhout, “Eduard Strasburger (1844–1912),” in Daedalus, 51 (1916), 927–928: G. Tischler, “Eduard Strasburger,” in Archiv für Zellforschung, 9 (1913), 1–40; and Georg Uschmann, Geschichte der Zoologie und der zoologischen Anstalten in Jena 1779–1919 (Jena, 1959), 60–61, 67–69.
A contemporary account of Strasburger’s and his colleagues’ botanical work is Sydney Howard Vines, Lectures on the Physiology of Plants (Cambridge, 1886), 658–660. A valuable overview placing Strasburger’s cytological contributions in the context of his time is William Coleman, “Cell, Nucleus, and Inheritance: An Historical Study,” in Proceedings of the American Philosophical Society, 109 (1965), 124–158, esp. pp. 126, 128–133, 145, 149–151, for Strasburger’s work and the development of his thought on the cell. Further background is Arthur Hughes, A History of Cytology (London, 1959), 62–63, 65–66, 71–72, 82, 134.