Note 20 — Chapter XVI · CAUSES WHICH INTERFERE WITH THE FREE CROSSING OF VARIETIES—INFLUENCE OF DOMESTICATION ON FERTILITY.
Reading edition
Kölreuter first observed this fact, ‘Mém. de l’Acad. de St. Petersburg,’ vol. iii. p. 127. See also C. K. Sprengel, ‘Das Entdeckte Geheimniss,’ s. 345.