In Pursuit of the Gene

PANGENES © 79
pangene was in fact responsible for the appearance of a monstrosity, he reasoned,
then it ought to be possible to transfer the monstrosity-causing
pangene from one variety to another. For his model system, he chose the
exotic poppy Papaver somniferum polycephalum, valued for the strange beauty of
its large crown of extra fruits surrounding the central capsule, which were
caused by the conversion of stamens to pistils (male parts to female). In
1893 he formed a hybrid between a polycephalous black-flowered poppy
(the variety known as mephisto) and a normal white-flowered variety (known
as Danebrog). If the polycephalous monstrosity was caused by a pangene,
De Vries reasoned, it ought to be possible to transfer the polycephalouscausing
pangene of the black-flowered variety to the white-flowered one by
crossing.
As it turned out the experiment was a success, clearly demonstrating
that the monstrosity was heritable and could be passed from one variety
to another. 16 De Vries noted the relative numbers of white- and blackflowered
poppies among the progeny of the hybrid in a brief aside. In later
years, he would claim that it was the data on flower color from the poppy
crosses that had led him to independently discover the laws of Mendelian
segregation, and would point to the nearly perfect 3:1 ratio of black- to
white-colored flowers among the progeny of the hybrid as evidence of his
prescience, but the real progression of his ideas was far less direct and considerably
more interesting.
In fact, it was De Vries’s encounter with statistics and probability that
triggered the line of inquiry that would lead him to the brink of Mendelism.
Like Galton, De Vries had been won over to the statistical approach by
Adolphe Quetelet, whose work he learned about at a conference in 1887,
where a Ghent botanist, named Julius MacLeod, whose father had corresponded
with Quetelet, read his paper on the statistical analysis of flower
fertilization. 17 MacLeod led De Vries to read Quetelet’s Anthropométrie ou mesure
des différentes facultés de l’homme, which emphasized the appearance of the
normal distribution in human traits, as well as in the traits of plants and
animals.
In a paper of 1890, De Vries showed that the number of rows in ears of
corn followed a normal distribution, and the following year he did a statis-