58 PLANT HYBRIDIZATION BEFORE MENDEL 



The remainder of the crossing experiments reported upon in 

 Kolreuter's third "Fortsetzung" are as follows: A cross between 

 Datura ferox ft. alb. and D. tatula fl. viol., a back-cross of Mira- 

 bilis jalapa (yellow), upon M. jalapa red X yellow. A reciprocal 

 cross is reported between Cheiranthus (Matihiola) incana and 

 Ch. annuus, between Sida cristata minor X major; Cucurbita of 

 a small round variety with few, small seeds, by a large Cucurbita 

 pepo, and a cross between Aquilegia vulgaris X canadensis and 

 its reciprocal. 



In the Datura cross, involving purple flower-color in D. tatula, 

 the flowers of the hybrid are reported as being "whitish-violet." 

 The Mirabilis back-cress is reported as giving the yellow color 

 in a stronger degree than in the ¥^. The Cheiranthus (Matthiola) 

 cross is interesting because of the genuine genetic purpose for 

 which it was undertaken. 



Kolreuter remarks: 



"since the essential difference which one believes to exist between 

 winter and summer stocks always seemed to me suspicious ; I therefore 

 concluded to completely decide this hitherto doubtful matter through 

 the experiment of crossing." (p. 200.) 



From these crosses, he raised in 1764, twelve plants from the 

 first, and six from the reciprocal cross. These were in all respects 

 like one another. Their intermediate character showed itself espe- 

 cially in the fact that they began to bloom earlier and more 

 vigorously than the winter stocks are accustomed to do in the 

 first year, and on the other hand brought their flowers out 

 later, and not in the complete numbers that the summer stocks 

 are accustomed to do. 



The Sida cross is reported as giving a hybrid intermediate in 

 color, form, and size of all the parts, between the two parents. 

 The Cucurbita cross likewise gave a complete intermediate. 



An interesting discussion follows of the sensitivity of the sta- 

 mens in flowers of Opuntia, Berberis, and Cistus. The last pages 

 of the third "Fortsetzung" (252-63) are taken up with a discus- 

 sion of further experiments on the pollination and fertilization 

 process. 



"since there are some people," he says, "who have brought into doubt 

 the organic structure of the pollen, assumed by me in the 'Vorlauf. 

 Nachr.' Sec. 5, I therefore hold it as my duty to help them out of their 

 dream in this respect, and to give a somewhat closer explanation of this 

 matter." (p. 252.) 



