PLANT HYBRIDIZATION BEFORE MENDEL 323 



De Vries {letter of December 18, 1924) : 



"when preparing my book on the Mutation Theory, I worked on the 

 basis of Darwin's Hypothesis of Pangenesis, and of the version of it 

 proposed in my Intracellular Pangenesis. The main principle of Pan- 

 genesis is the conception of unit characters. This led on the one side to 

 the theory of the origin of species by means of mutations, and on the 

 other to the description of the phenomena of hybridization as recom- 

 binations of these units. In 1893, I crossed Oenothera lamarckiana with 

 O. lam. brevistylis, and found their progeny to be uniform, and true to 

 the specific parent in 1894, but splitting in the second generation 1895, 

 giving 17-26 individuals with the recessive character (Mut. The. 11, p. 

 157). Many other species were tried with the same result, and dihybrid 

 crosses showed the laws of chance to be valid for them also. After finish- 

 ing most of these experiments, I happened to read L. H. Bailey's 'Plant 

 Breeding' of 1895.1 In the list of literature of this book, I found the 

 first mention of Mendel's now celebrated paper, and accordingly looked 

 it up and studied it. Thereupon I published in March 1900 the results of 

 my own investigations in the Comptes Rendus de I'Academie des Sciences, 

 T. CXXX, p. 845, under the title of 'Sur la loi de disjonction des hybrides,' 

 and shortly afterwards, in the same year, in the Berichte der deutschen 

 botanischen Gesellschaft, T. XVIII, p. 83, (March 14, 1900). A full account 

 of my experiments was given in the second volume of the German edi- 

 tion of my Mutation Theory, 1903." 



The paper of De Vries, "Sur la loi de disjonction des hybrides," 

 appearing in the Comptes Rendus for March 26, 1900, states 

 quite briefly results similar to those of Mendel, but obtained an- 

 terior to the author's re-discovery of the Mendel paper. 



Although from the printed volumes of the Comptes Rendus 

 and of the Berichte d. d. bot. Gesellschaft it appears that the 

 longer and fuller article, in German, in the latter, was received 



1 Professor Bailey's account of the manner in which the reference to 

 Mendel's paper came to be included in his book on "Plant Breeding," is 

 found in a footnote to "Plant Breeding" by L. H. Bailey, 4th ed., 1908, 

 p. 15" 5", as follows : 



"The following extract from a recent letter from Professor De Vries 

 (printed here by permission) will explain the reference in the text. 'Many 

 years ago you had the kindness to send me your article on Cross-Breeding 

 and Hybridization, of 1892; and I hope It will interest you to know that 

 it was by means of your bibliography therein that I learnt some years 

 afterwards of the existence of Mendel's papers, which now are coming 

 to so high credit. Without your aid I fear I should not have found them 

 at all.' " Professor Baily concludes : 



"My reference to Mendel in the bibliography referred to was taken 

 from Focke's writing. I had not seen Mendel's paper. The essay, 'Cross- 

 Breeding and Hybridization,' forms Chapter II of the present book; but 

 the bibliography that accompanies it was not printed until the second 

 edition of the book." 



