Cleland, Ralph Erskine

views updated


(b. LeClaire. Iowa, 20 October 1892; d. Bloomingtom Indiana, 11 June 1971)

botany, genetics.

The concept of mutation as the basis of evolutionary change had its origin in Hugo de Vries’s studies of Oenothera, the evening primrose. The validity of the mutation theory was challenged, however, when it was realized that the breeding behavior of Oenothera is atypical. Although Oenothera was much studied by the early geneticists, its genetic nature remained largely a puzzle until Ralph Cleland elucidated the unique cytogenetic mechanism that lay at its basis.

Cleland was the son of Edith Collins Cleland and Charles Samuel Cleland. When he was eighteen months old, his father, a United Presbyterian minister, accepted a call from a church in Philadelphia. Cleland grew up in a low-income urban neighborhood but spent the summers at a cottage in rural Pennsylvania, where he developed his interest in botany and natural history.

After being educated in the Philadelphia schools, Cleland received a four-year scholarship to the University of Pennsylvania, where he majored in the classics and took several courses in botany. Upon receiving the A.B. in 1915, he accepted the offer of a graduate assistantship in the department of botany, where he pursued the Ph.D. under the direction of B. M. Davis. His dissertation, completed in 1918, was a cytological study of the life history of the red alga Nemalion multifidum. Immediately after submitting his dissertation for publication, Cleland was inducted into the army and sent to France with a field artillery unit. In a matter of weeks the armistice was signed, and he returned to the United States. He was discharged from the army in April 1919. He married Elizabeth P. Shoyer on 11 June 1927; they had three sons.

After obtaining an instructorship at Goucher College that began in the fall of 1919. Cleland was at loose ends for the summer and offered to assist Davis with his Oenothera work. He chose Oenothera franciscana, a strain that happened to be at hand, to determine the best methods of fixation and staining for cytological study. His cytological preparations turned out to be of greater interest than a mere test of technique, revealing that four of the fourteen chromosomes regularly formed a closed circle at meiosis. This observation launched a series of studies that were of major importance in solving the genetic enigma presented by Oenothera.

The meticulous genetic analysis of Oenothera published by Otto Renner in 1917 first demonstrated that many species of Oenothera are permanent heterozygotes, so maintained by balanced lethal factors. Cleland’s initial study of Oenothera franciscana was the first step toward explaining the physical basis of the mechanism that Rennner’s analysis had revealed. Cleland’s subsequent studies during the 1920’s showed that chromosome circles were widespread in the various strains of Oenothera and that the atypical breeding behavior of Oenothera could be understood in terms of its unique chromosomal mechanism.

In the academic year 1927–1928, a Guggenheim fellowship enabled Cleland to spend a year in collaborative efforts with the German Oenothera workers Priederich Oehlkers and Otto Renner. This resulted in convincing evidence that the number of linkage groups in various races of Oenothera she therefore appeared to sym-bolize the solitary woman shut off from the world. But in essence she was precisely correlated with the number of pairs and/or circles of chromosomes at meiosis. Here was rigorous proof of the correlation between gene and chromosome behavior.

When John Belling explained circle formation in Datura stramonium as the result of exchanges of segments between nonhomologous chromosomes, Cleland recognized that this concept of segmental interchange could be applied to Oenothera, He developed a scheme in which the chromosome complement of each Oenothera strain could be identified by the arrangement of its fourteen chromosome ends. He showed that if the arrangement of two genomes was known, when they were combined in a hybrid, the chromosome configuration at meiosis of the hybrid could be predicted.

Further, Cleland recognized that similarity in the segmental arrangement of the genomes in different strains of Oenothera could serve as an index of phylogenetic relationship. Thus, during the remainder of his research career he carried out a cytogenetic analysis of more than three hundred collections from natural populations of Oenothera. This led to the characterization of the different groups of North American Oenothera species and their evolutionary relationships. These studies, extending over nearly thirty years, are summarized in Oenothera: Cytogenetics and Evolution (1972). which Cleland com pleted just before his death in 1971.

In 1938 Cleland left Goucher College to assume the chairmanship of the department of botany at Indiana University, where he remained for the rest of his life. From 1950 to 1958 he served as dean of the Graduate School. Cleland’s research career of some fifty years was characterized by consistently significant publications. His distinction in research brought him national recognition and election to leadership positions in professional scientific societies. He was a member of the National Academy of Sciences, the American Philosophical Society, and the American Academy of Arts and Sciences. He served as president of the Genetics Society of America, the Botanical Society of America, the American Society of Naturalists, and the Indiana Academy of Science. Cleland held honorary degrees from Hanover College, the University of Pennsylvania, and Indiana University. Other honors included the John F. Lewis Award of the American Philosophical Society, the Golden Jubilee Merit Citation of the Botanical Society of America, and honorary membership in the Genetics Society of Japan and the Botanical Society of Korea.

Essentially a modest man, Cleland had a calm, unruffled approach to problems that inspired confidence in his judgment, He was a conscientious teacher who set high standards for his students, and willingly taught at the introductory as well as at the graduate level. In spite of a busy schedule he was never impatient or short of time when students consulted with him, Retirement brought little change in Cleland’s activities. He remained active in research and continued to participate in academic and scientific affairs until his death.


I. Original Works. Cleland’s scientific writings include “The Reduction Division in the Pollen Mother Cells of Oenothera franciscana,” in American Journal of Botany. 9 (1922), 391–413; “Chromosome Behavior During Meiosis in the Pollen Mother Cells of Certain Oenotheras,” in American Naturalist, 59 (1925), 475–479: “The Genetics of Oenothera in Relation to Chromosome Behavior. with Special Reference to Certain Hybrids,” in Zeitschrift für induktiv Abstammungs- und Vererbungslehre supp. vol. 1 (1928). 554–567; “Erblichkeit und Zytologie verschiedener Oenotheren und ihrer Kreuzunge,” in Jahrbuch der wissenschaftliche Botanik. 73 (1930). 1–124. written with Friedrich Oehlkers; Interaction Between Complexes as Evidence for Segmental Interchange in Oenothera.’ in Proceedings of the Nationl Academy of Sciences, 16 (1930). 183–189. written with Albert F. Blakeslee: “Analysis of Wild American Races of Oenothera (Onagra),” in Genetics. 25 (1940}, 633–644: “Phylogenetic Relationships in Oenothera.” in Proceedings of the Eighth International Congress of Geneitics, Hereditas (1949), SV 173–188; and Oenothera: Cytogenetics and Evolution (New York, 1972), A personal memoir is Recollections: The Early Years (Bloomington, Indiana, 1974).

II. Secondary Literature. The most complete account of Cleland’s life and work is Erich Steiner, “Ralph Erskine Cleland,” in Biographical Memoirs. Notional Academy of Sciences. 53 (1982). 120–139, with a complete bibliography.

Erich Steiner