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GENETICS IN SWEDEN
BY
Dr. NILS H ERI BER T=N ILSSO N
LECTURER, LUND
The swedish school of experimental genetics made
its start before the rediscovery of the Mendelian law. A pre«Mendelian
geneticist, Pehr Bolin, at that time assistant at the plant breeding institute
in Svalöv, published in 1897 a paper dealing with artificial crosses between different
varieties of barley in »Utsädesföreningens Tidskrift». He arrived at the conclusion
that no variation takes place in the first generation, while it does occur in the
second. This variation seems to follow definite laws, he says, as the resulting
varieties represent different combinations of parent characters. He has also found
that the variation in certain cases fails beyond the limits of the variation of the parent
plants. He knew the faet of combination, as did many of the pre*Mendelian
workers, but he did not push his knowledge to the point of exact numerical
relations. The value of Bolin’s discovery does not seem to have been appreciated
at that time, and his name has not been mentioned in the foreign literature among
the pre«Mendelian workers, so fas as I know. This is explained by the circum*
stance that his paper is written in Swedish and published in a journal of applied
science.
The first who made Mendel’s discovery known in Sweden was the talented
plant physiologist in Lund, Bengt Lidforss. He had been mueh interested in the
mutation theory of Hugo de Vries, and he acquainted himself with Mendel’s
discovery in that work. Mendel’s discovery was considered as mainly a verifica*
tion of the mutation theory at that time, as it demonstrated in a clear way the
discontinuity and the constancy of the characters. He gave a masterly summary
of Mendel’s discovery in a popular work published 1904. He had already at this
time investigations under way dealing with the problem of the origin of species
in the genus Rubus. He found that species originated through mutation as well
as through hybridization. Some species, as R. polyanthemus, gave rise to a great
number of morphologically different types when selfed, which formed an absolute
parallel to the mutations of de Vries in many cases. A still greater variation,
however, was obtained from the hybridization experiments. The hybrid caesius
X Wahlbergii, for instance, gave so great a variation in the second generation
that he was able to distinguish types among the descendants which resembled
nine species already described. There were additional types which did not resemble
any known species. These striking results led him to adopt the Mendelian point
of views more and more. He dismisses at last the mutation theory entirely and
holds the view that the seemingly spontaneous, wild forms represent the last
oscillations of a segregation. His discovery that in certain cases of successful
species Crossing all the descendants resemble the female parent plant is very in«
teresting. The pollination stimulates the development of the ovules, according to
the explanation given by Lidforss, but does not bring about any nuclear fusions.
L.
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