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RALPH ERSKINE CLELAND
October 20, 1892-fune 11, 1971
BY ERICH STEINER
MUCH OF THE WORK that lecI to the establishment of
genetics as a distinct biological (discipline involved
studies of Oenothera, the evening primrose. The concept of
mutation, which remains central to the dogma of genetics,
had its origin in the observations of Hugo deVries on
Oenothera. deVries's mutation theory was challenged,
however, when it became clear that Oenothera exhibited a
breeding behavior that clid not conform to that of other or-
ganisms. It took some thirty years before the genetic nature
of Oenothera was fully explained. Ralph Cleland ma(le a major
contribution to the solution of this long-puzzling problem
through his discovery of chromosomal ring formation at
meiosis and the subsequent proof that it is the physical basis
of the atypical breeding behavior of Oenothera.
Ralph Erskine Cleland was born in LeCIaire, Iowa on
October 20, IS92, the first chilct of Charles Samuel and Edith
Collins ClelancI. The family was of Scotch-Irish ancestry on
both sides. Ralph's father, who spent his childhood on a farm
in Minnesota, was a minister of the Uniter! Presbyterian
Church; his mother came from a family of farmers in Ohio.
When Ralph was one-anct-a-half years oIcT, his father ac-
ceptecl a call from a church in downtown Philadelphia, the
pulpit of which he was to occupy for forty-five years. Charles
121
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122
BIOGRAPHICAL MEMOIRS
Clelanc! became active in denominational affairs, serving a
term as moderator and spending many years as secretary of
the Foreign Mission Board, an assignment that lect him to
travel extensively in Africa, the MicicIle East, and Inctia.
Ralph grew up in a low-income, urban neighborhood}
where his playmates were largely children of factory workers.
Ralph's father, however, insisted that the children spend
their summers at a country cottage in Lehigh County, Penn-
sylvania. It was here that Ralph cleveloped his interest in
botany and natural history, spending much of his time roam-
ing through the fields and wools.
In Philadelphia, Ralph attencled Central High School
where he was enrollecI in the "classical" course. He con-
sidered his high school education unusual in that it was to
some extent the equivalent of a college program. The cur-
riculum was broactly liberal arts, the courses rigorous, and he
was taught by men with recognizes] standing in their clisci-
plines. He entered the University of Pennsylvania with a
four-year scholarship, receiving acivancec! credit for some of
his high school work. He selected classics as his major ant!
history as a minor, but he also took several courses in botany.
During his unclergraduate years Ralph engaged in a number
of extra-curricular affairs, including participation in plays,
debating, sports, the editorial board of the yearbook, ant!
membership in the literary society. He believed that the latter
activity contribute<] in particular to his social development
cluring the college years. Undergraduate honors includecl
prizes in Greek and botany and election to Phi Beta Kappa.
In addition to his college studies and activities, he worked
in the social programs of his father's church, an experience
that impressed upon him the damaging social effects of alco-
hol and led him to become a lifelong teetotaler.
Upon graduation from the University, Cleland was of-
fered an assistantship in the Department of Botany, even
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RALPH ERSKINE CLELAND
123
though his course preparation in biology was minimal.
Nevertheless, by working summers, anc} with the air] of a
Harrison Fellowship for two years, he was able to complete
the requirements for the Ph.D. in three years. His doctoral
research was carried out under the direction of Professor
B. M. Davis, whose interests centered on cytological studies of
the algae and the cytogenetics of Oenothera. Cleland chose to
work on the cytological life history of a recT alga, Nemaition
multifidum. As a result, he spent his summers at Woods Hole
where he was able to extent! his acquaintance with other
biologists. In July of lL91S, upon mailing his thesis to be
published, he returnee] home to find an order to report for
induction into the military service. After five weeks of train-
ing, he was sent to France with a fielcI artillery unit. Shortly
after his arrival abroad, he was hospitalized with influenza.
By the time he recovered, the armistice had been signed and
he returnee] to the United States to be dischargecI from the
army in April 1919.
Ralph Cleland's research career had its origin in a set of
fortuitous circumstances. Shortly after his discharge from the
army, he obtained an appointment as an instructor in biology
at Coucher College, to begin in the fall of 1919. Without a
commitment for several months, Clelanct offered to assist
Professor B. M. Davis with his research. Dr. Davis was at the
moment interested] in the cytology of the hybrid between a
diploic! and tetraploicI race of Oenothera ant! turned the prob-
lem over to Cleland. Cleland chose Oenothera franciscana, a
strain that happened to be at hand, for determining the best
methods of fixation and staining. The stucly of Oe. franciscana
proved to be of greater interest than a mere test of technique,
since the cytological preparations revealed that four of the
fourteen chromosomes regularly formed a closet! circle at
meiosis. This observation led to a series of studies by Cleland
that were of major importance in elucidating the puzzling
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124
BIOGRAPHICAL MEMOIRS
genetic behavior of Oenothera, a problem that had remained
largely unsolved since it first came to light as a result of
studies of the genus by Hugo cleVries at the turn of the
century.
Hugo (leVries, a Dutch plant physiologist, initiated
studies of variation in Oenothera in T885, hoping to attack
problems of evolution through an experimental approach.
His results led to the publication in 1900 of The Mutation
Theory,* in which he proposed that evolution of new species
occurred through su~clen and spontaneous changes in one or
more hereditary characters. Evidence for his theory came
largely from observations of Oenothera; it was quickly ap-
parent that the concept of mutation could only be valid if the
strains alleged to be undergoing mutation were pure species.
Were the strains of hybrid nature, then such variations,
which cleVries called mutations, could simply be recombi-
nants. The problem arose because strains of Oenothera bred
true when self-pollinaterl, but behaved as hybrids when out-
crossed. It was thus essential to establish the purity of the
Oenothera species before the mutation concept couIcl be con-
sidered valid and thus significant for evolutionary theory.
The contradictory behavior of Oenothera remained! a puz-
zle that attracted a great many investigators in the early
1900's, but their efforts met with little success until the me-
ticulous genetic analysis of Otto Renner, published ire 1917,
which clemonstrated that many of the oenotheras were per-
manent heterozygotes persisting in this condition because of
balanced lethal factors. Ralph ClelancI's stucly of Oenothera
franc~scana appeared in 1922 ant! was the first step toward
the explanation of the physical basis of the mechanism re-
vealecl by Renner's brilliant analysis. The curious fact is that
* H. deVries, Die Mulationstheorie (Leipzig: Von Veit; vol. I, 1901; vol. 2, 1903);
The Mutation Theory (English translation, Chicago: Open Court; vol. 1, 1909; vol. 2,
1910).
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RALPH ERSKINE CLELAND
125
numerous cytological studies of Oenothera had been carried
out cluring the previous two decades, yet no one had recog-
nized that the formation of chromosome rings at meiosis was
an unusual and constant feature of most of the Oenothera
. . . .
strains uncler Investigation.
The paper on Oenothera franciscana floes not place em-
phasis on the discovery of chromosomal ring formation;
more attention is focused on the evidence for the purity of
Oenothera franciscana ant! the general importance of species
purity for the Oenothera problem. The next paper published
by Cleland appeared! in the American Naturalist in 1923 and
hac! an entirely different orientation. In the interim Cleland
tract examined the meiotic clivision in several other strains of
Oenothera and discovered that each had a characteristic
chromosomal configuration involving circles of various sizes.
He noted that the adjacent members in a circle of chromo-
somes appear to go to opposite poles, an arrangement not
likely to depend purely on chance. Further, if one assumes
that homologous chromosomes go to opposite poles, then
circle formation could explain the genetic results of Shull,
who hac! concluded that all the genes in Oenothera belong to
a single linkage group.
Cleland's studies of the following years extencled the
number of Oenothera strains examined. He establisher! that a
wide range of chromosomal configurations occur and each
remains constant for a particular strain. Moreover, it was
recognizes! that some mechanism must exist to give the regu-
lar arrangement of the chromosomes in the circle that leads
to alternate segregation at the time of the division. Neverthe-
less, at this time CIelanc! still believed that the chromosomes
in the circle were unpaired; thus he failer! to recognize the
cause of circle formation.
Not until the 1926 paper on meiosis in Oenothera biennis
and Oe. biennis sulfured d id Clelanc! specifically cite Renner's
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126
BIOGRAPHICAL MEMOIRS
work and utilize the balanced lethal concept to explain the
genetic behavior of Oe. biennia. It is clear that by this time
Cleland was fully aware of the direct relationship between the
unique chromosomal situation and the atypical genetic be-
havior of Oenothera; a coherent hypothesis still remained to be
developed, however.
The award of a Guggenheim Fellowship made it possible
for Cleland, accompanies! by his recent bridle, Elizabeth, to
spenc! the summers of 1927 and 1928 as well as the inter-
vening academic year in Germany in collaborative efforts
with Friederich OehIkers, Otto Renner, and Hugo cleVries. A
major study aimed at correlating the chromosome configura-
tions in various races of Oenothera and their hybrids with their
breeding behavior was undertaken with Dr. OehIkers. In this
project Clelanct assumed responsibility for the cytological
work, while OehIkers carried out the genetic studies. The
1- · 1. ~ . ~ 1 . ~ · . ~ ~
.
preliminary results or one wore were reported in tneAmer~can
Naturalist in ~ 929; this was followed by a full account in ~ 930
in the fahrbuch fur Wissenschaftliche Botanik. These articles
presented convincing evidence that races of Oenothera ex-
hibiting a circle of fourteen chromosomes at meiosis trans-
mittecl the genes in single groups; the hybrids, on the other
hancI, showed diverse configurations at meiosis, but with each
hybrid constant in its configuration. Further, the number of
linkage groups was shown to be precisely correlated with the
number of pairs anchor circles of chromosomes at meiosis.
Here was rigorous proof of the correlation between gene
and chromosome behavior. While the breeding behavior of
Oenothera could now be understood in terms of its unique
chromosomal mechanism, questions regarding the nature
anti distribution of the chromosomes still needed! to be
answered. Cleland did not offer an explanation for the for-
mation of the chromosomal circles. He continued to consider
the chromosomes within a circle as essentially unpaired and
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RALPH ERSKINE CLELAND
127
as examples of telosynapsis (association of the ends of chro-
mosomes), a concept that later proved to be incorrect.
The explanation for circle formation was first suggested
by John Belling in a 1927 paper dealing with various types of
chromosome configurations observer! in Datura stramonium.*
Among these was a circle of four chromosomes, the members
of which could be identifiec! morphologically ant! thus recog-
nized as nonhomologous. Belling reasoned that an exchange
between two nonhomologous chromosomes hacl occurred,
and that such a plant, possessing two original chromosomes
and two that hac! interchanged segments, would exhibit a
circle of four chromosomes as a result of their pairing re-
quirements. The concept of segmental interchange! was the
element needed to solve the last major question of the
Oenothera behavior.
Further, the concept of segmental interchange led Cle-
lanc] to recognize that chromosome configuration couIct serve
as an index of similarity in segmental arrangement, pairs or
small circles of chromosomes indicating that two complexes
are identical or similar while a circle of fourteen chromo-
somes signifies the greatest clegree of dissimilarity between
the two complexes. This suggested that chromosomal end
arrangement might be useful as a measure of phylogenetic
relationship anti thus lead to an understanding of the evolu-
tionary history of the group. The genus Oenothera hac! long
been a problem for taxonomists because of the large number
of intergrading forms that hybridize freely. Cytogenetic
analysis showed promise for identifying phylogenetic group-
ings, which then might be a basis for a more satisfactory
taxonomic treatment of the genus.
* J. Belling, "The Attachment of Chromosomes at the Reduction Division in
Flowering Plants," Journal of Genetics, 18(1927): 177-205.
t More commonly called reciprocal translocation.
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BIOGRAPHICAL MEMOIRS
A study of collections from natural populations through-
out California initiates! this new direction of Cleland's work,
which was to become the main thrust of his research for the
remainder of his career. Following study of the California
races, the work expanded into a cytogenetic analysis of large
numbers of Oenothera collections from throughout North
America; the objective was to understand the genetic ant!
chromosomal structure of natural populations anct thereby
trace their evolution.
In 1938 Cleland left Coucher College to assume the chair-
manship of the Department of Botany at Tncliana University.
Here his research program on Oenothera population structure
gained momentum with the support of the Rockefeller
Foundation and with the aid of various research associates
ant! graduate students.
The progress of these studies was reported in a series of
papers beginning in 1940 with "Analysis of Wild American
Races of Oenothera (Onagra)," in which the various phylo-
genetic groups were identified anc! described in a provisional
way. The subsequent work by Cleland and his associates con-
centrated on the cytogenetic analysis of over 300 collections
and led to a more precise characterization of the different
groups and their evolution. These studies, which extended
over nearly thirty years, were summarizer! and reviewed in
Cleland's book, Oenothera: Cytogenetics and Evolution, com-
pleted shortly before his cleath.
While the main thrust of Clelanct's research in the latter
years took the direction of Oenothera population studies, he
also published a number of papers on such more-or-less un-
related genetic topics in Oenothera as chromosome structure
and behavior, incompatibility factors, and the inheritance of
cruciate petals. A number of these studies were carried out
during his retirement years. It is noteworthy that Clelancl's
scientific contributions extencled over a period of fifty years.
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RALPH ERSKINE CLELAND
129
His papers were consistently significant. As new problems
arose, he attacked them with success, focusing on the signifi-
cant and avoiding the trivial.
Clelancl's distinction in research brought him national
recognition and subsequent election to leadership positions
. . . . . . . ~ . .
In various processional sclentlilc societies as we . as numerous
honors and awards. He served on many national committees
clearing with scientific matters. In 1950 he assumer! the dean-
ship of the Graduate School of Indiana University, at the
same time continuing as chairman of the Department of
Botany. He held both positions until his retirement from
administrative duties in 1958. CIelancT 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, The Botanical
Society of America, the American Society of Naturalists, ant]
the Indiana Academy of Science. Other honors included the
first John F. Lewis Award of the American Philosophical
Society and the GoIclen Jubilee Merit Citation of the Botani-
cal Society. He was a corresponding member of the Deutsche
Botanische Geselischaft and an honorary member of the
Genetics Society of Japan and the Botanical Society of Korea.
Cleland helc! honorary degrees from Hanover College, the
University of Pennsylvania, and Indiana University.
ClelancT possesses! an unusual combination of personal
characteristics that undoubtedly played an important role in
the professional achievement he attained. In some respects
he seemed a shy man, yet he possessed a quiet self-assurance
that enabled him to present his research conclusions effec-
tively at a scientific meeting, even as a young scientist whose
work was just getting under way. In the early years, when he
undoubtedly carried a relatively heavy teaching loacl, he
devotecl his summers to research, and to growing, gathering,
and preparing material for study throughout the academic
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BIOGRAPHICAL MEMOIRS
year. His consistently significant research output was un-
cloubtecIly the result, not only of long hours, but of a per-
sistence and steady application to the task at hand. Neverthe-
less, he was always available to his students; he never gave
evidence of resentment or impatience at being interrupted.
His calm, unruffled personality enabled him to shift from
one activity to another with a minimal lag effect, using his
time efficiently. In later years, because of his involvement in
national scientific affairs, he traveler! to Washington on a
regular schedule and was often away from his laboratory as
much as he was there. He arranged his teaching scheclule to
adapt to these clemands, not infrequently returning to
campus only moments before his lecture.
Cleland had a high regard for the academic way of life,
and particularly for creative scholarship. The fact that his
three sons all chose academic careers was a great satisfaction
to him. He was a conscientious teacher who set high stan-
clarcls for his students. He willingly taught at the introductory
as well as at the graduate level. Although not a charismatic
speaker, he was nevertheless articulate, and his lectures were
well organized, accurate, anct up-to-date.
While many high achievers in science frequently have
fragile egos requiring continuous nurture, Clelancl obtained
his satisfactions from an inner conviction that his contribu-
tions were significant and sound He was essentially a modest
person, readily approachable, lacking any trace of an exag-
gerated sense of self-importance. He was always willing to do
a menial task when it was expedient. His concern and con-
sideration for others were shown not only in his personal
relationships but also in his support of programs that wouIct
contribute to the welI-being of the community as a whole. He
remained an active church member throughout his life.
While on occasion his students may have consiclered him a bit
straight-lacecl because of his opposition to smoking and alco-
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RALPH ERSKINE CLELAND
131
hoi, he nevertheless held their respect anct admiration. Ralph
and Elizabeth Cleland lived without ostentation. Their home
radiated a warm and comfortable atmosphere. They both
hac! a positive, optimistic, and cheerful attitude toward life
with an enthusiastic involvement in the affairs of the Univer-
sity, the community, and the world as a whole. This persisted
even after Mrs. Cleland became an invalicI.
Clelancl had a creep interest in music. For many years he
was a regular member of a group that assembler! in Alfred
Kinsey's home to listen to music in a serious way. Whenever
possible he attendee! the concerts and was prouct of the
quality of the musical offerings at Indiana University. It was
thus highly appropriate that the memorial service following
his death took the form of a concert.
After retiring from administrative posts at the age of
sixty-five, Cleland returned to teaching until complete retire-
ment at seventy. Subsequently he continuer! his research,
pursuing various problems that earlier had lower priority in
his research program. Ralph CIeland was the last survivor of
the investigators who hac! played a major role in the unravel-
ling of the Oenothera problem and who had had direct contact
with most of the prominent workers in the field initiated by
Hugo cleVries. It was thus particularly important that he
write a book reviewing the massive Oenothera literature and
providing an up-to-date critical summary of the Oenothera
work. In typical fashion, the project mover! ahead on
schedule and the manuscript was complete<] only a few (lays
before he was stricken with a heart attack in his laboratory.
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132
DEGREES
BIOGRAPHICAL MEMOIRS
HONORS AND DISTINCTIONS
A.B., University of Pennsylvania, 1915; M.S., 1916; Ph.D., 1919
Sc.D. (honorary), Indiana University, 1970
L1.D., Hanover College, 1957
ACADEMIC POSITIONS
Goucher College: Instructor of Biology (1919-1920~; Assistant Pro-
fessor (1920-19231; Associate Professor (1923-1930~; Professor
(1930-1938~; Chairman of Department (1937-1938)
Indiana University: Professor and Chairman, Botany Department
(1938-19581; Dean of Graduate School (1950-1958)
Instructor, University of Michigan, summer 1920
Instructor, Marine Biological Laboratory, summer 1925
EDITORIAL POSITIONS
Editor, Plant Cytology, Biological Abstracts, 1925-1972
Trustee, B iologacal A bstracts, 1943- 1948
Editor-in-Chief, A merican f ournal of B otany, 1940- 1946
Editorial Board, American Journal of Botany, 194~1953
AWARDS
Phi Beta Kappa
Sigma Xi
First John F. Lewis Award, American Philosophical Society, 1937
Golden Jubilee Merit Citation, Botanical Society of America, 1956
Guggenheim Fellowship, 1927-1928; Renewed, 1928
PROFESSIONAL AND HONORARY AFFILIATIONS
Fellow, American Association for the Advancement of Science
(Council at various times; Vice-President and Chairman of Sec-
tion G. 1944)
Fellow, Indiana Academy of Science (President, 1959)
Fellow, American Academy of Arts and Sciences
Member, Botanical Society of America (President, 1947)
Member, Genetics Society of America (Vice-President, 1955; Presi-
dent, 1956)
Member, American Society of Naturalists (Secretary, 1938-1940;
President, 1942)
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RALPH ERSKINE CLELAND
133
Member, Society for Study of Evolution
Member, International Society for Cell Biology
Member, American Philosophical Society
Member, National Academy of Sciences
Honorary Foreign Member, Genetics Society of Japan
Honorary Life Member, Botanical Society of Korea
Corresponding Member, Deutsche Botanische Gesellschaft
Organizing Committee, Member of Governing Board, and first
Chairman (1948-1949), American Institute of Biological
fir -
~clences
Chairman, Division of Biology and Agriculture, National Research
Council, 1948-1951
Chairman or Member of many NRC committees, including:
UNESCO Committee; Maize Committee;. Kimber Award Com-
mittee; Agricultural Board; NRC, NSF, and Fulbright Fellowship
panels or boards; Pacific Science Board; Advisory Committee.
Office of Scientific Personnel (Chairman); Advisory Committee,
International Organizations and Programs, Office of Foreign
Secretary
Member, Advisory Committee to Selective Service, 1951-1953
Member, U.S. National Commission for UNESCO, 1958-1960
Consultant, National Science Foundation, 1952-1959
Secretary-Treasurer, Association of Graduate Schools of the Asso-
ciation of American Universities, 1955- 1958
Chairman, American Delegation to 7th International Botanical
Congress, Stockholm, 1951
Member, American Delegation to 9th International Genetics Con-
· gress, Bellagio, 1953
Member, American Delegation to General Assembly, International
Union of Biological Sciences (IUBS), Nice, 1953
Vice-President, NUBS, 1953-1959
President, Genetics Section, 8th International Botanical Congress,
Paris, 1954
Sent with Farrington Daniels by the National Academy of Sciences
to Southeast Asia as "Scientific Ambassador," 1960; visited thir-
teen countries during three-month trip. Also served as consul-
tant for the Asia Foundation
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134
BIOGRAPHICAL MEMOIRS
B IBLIOGRAPHY
1917
A new Erythrotrichia from Woods Hole. Rhodora, 20: 141 ,15.
1919
The cytology and life history of Nemalion multifidum. Ann. Bot.,
33:323-52.
1922
The reduction division in the pollen mother cells of Oenothera fran-
ciscana. Am. I. Bot., 9: 3 9 1~ 1 3 .
1923
Chromosome arrangements during meiosis in certain oenotheras.
Am. Nat., 57:562-66.
1924
Meiosis in pollen mother cells of Oenothera franciscana sulfurea. Bot.
Gaz., 77:149-70.
1925
Chromosome behavior during meiosis in the pollen mother cells of
certain oenotheras. Am. Nat., 59:475-79.
1926
Meiosis in the pollen mother cells of Oenothera biennis and Oenothera
biennis sulfurea. Genetics, 11: 127-62.
Cytological study of meiosis in anthers of Oenothera muricata. Bot.
Gaz., 82: 55-70.
1928
The genetics of Oenothera in relation to chromosome behavior, with
special reference to certain hybrids. Z. Induk. Abstamm.
Vererbungsl., Suppl. Bd., 1: 55~67.
1929
Meiosis in the pollen mother cells of the oenotheras, and its prob-
able bearing upon certain genetical problems. Proc. Int. Congr.
Plant Sci., 1:317-31.
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RALPH ERSKINE CLELAND
135
Chromosome behavior in the pollen mother cells of several strains
of Oenothera lamarckiana. Z. Induk. Abstamm. Vererbungsl., 51:
12~45.
With F. Oehlkers. New evidence bearing upon the problem of the
cytological basis for genetical peculiarities in the oenotheras.
Am. Nat., 63:497-510.
Die Zytologie der Oenothera-Gruppe biennis in ihrem Verhaltnis zur
Vererbungslehre. Tubinger Naturwiss. Abhandlungen, 12:
50-55.
1930
With A. F. Blakeslee. Interaction between complexes as evidence
for segmental interchange in Oenothera. Proc. Natl. Acad. Sci.
USA, 16:183-89.
With A. F. Blakeslee. Circle formation in Datura and Oenothera.
Proc. Natl. Acad. Sci. USA, 16:177-83.
With F. Oehlkers. Erblichkeit und Zytologie verschiedener Oeno-
theren und ihrer Kreuzungen. Jahrb. Wiss. Bot., 73: 1-124.
1931
Cytological evidence of genetical relationships in Oenothera. Am. I.
Bot., 18:629-40.
The probable origin of Oenothera rubricalyx "Afterglow" on the basis
of the segmental interchange theory. Proc. Natl. Acad. Sci.
USA, 17:437-40.
With A. F. Blakeslee. Segmental interchange, the basis of chromo-
somal attachments in Oenothera. Cytologia, 2: 175-233.
1932
Further data bearing upon circle formation in Oenothera, its cause
and genetical effect. Genetics, 17: 572-602.
1933
Predictions as to chromosome configuration, as evidence for seg-
mental interchange in Oenothera. Am. Nat., 67:407-18.
With O. Renner. Zur Genetik und Cytologie der Oenothera chica-
ginensis und ihrer Abkommlinge. Z. Induk. Abstamm. Verer-
bungsl., 66:275-318.
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136
BIOGRAPHICAL MEMOIRS
1934
With W. H. Brittingham. A contribution to an understanding of
crossing over within chromosome rings in Oenothera. Genetics,
19:62-72.
1935
Chromosome configurations in Oenothera (grandif iora x lamarcki
anal. Am. Nat., 69:46~68.
Cytotaxonomic studies on certain oenotheras from California.
Proc. Am. Philos. Soc., 75:339-429.
Hugo deVries, 1848-1935. J. Hered., 26:289-97.
1936
Hugo deVries. Proc. Am. Philos. Soc., 76:240-50.
Peculiarities of chromosome and breeding behavior in the evening
primrose. Teach. Biol., 6:119-24.
Some aspects of the cytogenetics of Oenothera. Bot. Rev., 2:316-48.
1937
Species relationships in Onagra. Proc. Am. Philos. Soc., 77:477-542.
William Harding Longley. Science, 85:400-401.
1940
David M. Mottier. Science, 91:423-24.
Analysis of wild American races of Oenothera (Onagra). Genetics,
25:63~44.
1942
The origin of bJecipiens from the complexes of Oenothera lamarckiana
and its bearing upon the phylogenetic significance of similarities
in segmental arrangements. Genetics, 27:55-83.
1943
John Muirhead Macfarlane. Yearb. Am. Philos. Soc., 1943:408-11.
1944
The problem of species in Oenothera. Am. Nat., 78:5-28.
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RALPH ERSKINE CLELAND
1946
137
With M. Newcomb. The growth of Oenothera plants from embryos
cultured in vitro. Proc. Indiana Acad. Sci., 55:36.
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