PLANT HYBRIDIZATION BEFORE MENDEL 337 



out, that in crosses between maize races I had found very interesting but 

 very complicated relationships. That other investigators also worked in 

 the same direction I naturally did not know, otherwise I would have 

 hastened more with the preparation of the publication. 



"On the morning of the 21st of April, 1900, I received a separate 'Sur 

 la loi de disjonction des hybrides,' of De Vries, and by the evening of 

 the 22nd of April, my contribution, 'G. Mendels Regel iiber das Ver- 

 halten der Nachkommenschaft der Bastarde,' was ready. I sent it to the 

 German Botanical Society in Berlin, where it was received April 24, and 

 was reported in the session of April 27. The issue in question of the 

 'Berichte' appeared at the end of May, about the 25th. The contribution 

 has been again printed in the volume in which the German Society for 

 the Science of Heredity has recently collected my genetic works, insofar 

 as they have not appeared independently anew. 



"For that matter, I do not lay too much weight upon the re-discovery 

 itself. According to my opinion, it was important that the Mendelian 

 laws should finally be known and verified. Whether it happened by their 

 being independently found anew, or through the fact that someone first 

 read the memoir of Mendel, and then repeated the experiments, is, how- 

 ever, at bottom, an indifferent matter for science. It was accordingly only 

 a confirmation of what had been discovered more than 30 years before. 

 And through all that in the meantime had been discovered and thought 

 (I think above all of Weismann), the intellectual labor of finding out 

 the laws anew for oneself was so lightened, that it stands far behind the 

 work of Mendel. I myself should prefer, for my part, to lay more weight 

 upon my later works, e.g., the Bryonia experiments." 



In response to further inquiry, Professor Correns' reply is as 

 follows (letter of January 30, 1925) : 



"I did not discover the constant relationship [Gesetzmassigkeit] in 

 Pisum alone but in Zea and Pisum simultaneously. In the publication, I 

 placed Pisum in the foreground on Mendel's account, and out of didactic 

 considerations. That I, however, also experimented with Pisum almost 

 from the beginning, is explained from the way in which, as a matter of 

 fact, I arrived at my genetic investigations. Originally I started out to 

 solve the xenia question. To this end I wished to test experimentally all 

 the assertions known in the literature. I began (1894) with Phaseolus 

 vulgaris nanus (with which, however, cross-fertilization did not succeed 

 at all for me), then with Zea, Pisum, Lilium and Matthiola. This is all 

 related in my 'Crosses between maize races, with particular reference to 

 xenias,' Bibliotheca Botanica, Heft 53 (1902), where the results are also 

 mentioned ; those upon Matthiola were also published previously in an- 

 other place. For Pisum there are different pertinent assumptions. One 

 only needs refer, for example, to Darwin, 'The variation of animals and 

 plants under domestication,' and to Focke. Unfortunately Focke here, 

 in the case of xenias, does not mention Mendel, otherwise I should 

 have probably read his work immediately at the beginning of my in- 

 vestigations. After I had carried on cross-fertilizations with Pisum like- 

 wise on account of the xenia question (there exist, indeed, assumptions 

 on the influence of the seed-coat), it was I suppose, quite natural to 

 grow the crosses themselves, as I did not only with Pisum, but also 



