50 PLANT HYBRIDIZATION BEFORE MENDEL 



And again : 



"Hence I believed myself, by virtue of the contrary outcome of my 

 experiments, to be justified rather in holding the oft-mentioned oily 

 secretion for a conduction medium, than to set it up as a true fertiliza- 

 tion substance (Saamen)." 



In all, 49 experiments are detailed in Kolreuter's "Zweite 

 Fortsetzung," distributed over seven different genera, as follows: 



Nicotiana 30 Datura 2 



Dianthus 8 Mirabilis 2 



Verbascum 4 Leucojum 1 



Hibiscus 2 



Of the 30 Nicotiana experiments, eight were species-crosses ; 

 nine, experiments with one or more kinds of pollen; seven, ex- 

 periments to determine the nature of the stigmatic secretion ; two 

 were F-^'s back-crossed with one of the parents, and four were 

 compound crosses. The pollen and stigma experiments have been 

 described in detail. The species-crosses involved the species pani- 

 culata^ glutinosa^ rustica^ transylvamca^ and major ft. albo. There 

 is nothing distinctly interesting in these crosses per se. In the case 

 of paniculata X glutinosa it is stated that the hybrid combined 

 the characters of the two parents in the most exact manner. 

 ("Zeigte nebst den iibrigen Merkmalen offenbar an, dass sich die 

 Natur der $ mit der Natur der 5 auf's genaueste vereinigt haben 

 musste.") (p. 110.) Of the back-crosses on the Fj, of which two 

 are reported, in neither case is the number of the progeny suffi- 

 cient for generalization; being one, in the case of (A^. paniculata 

 X rustica) X paniculata^ and seven in the case of (A'^. pani- 

 culata X rustica) X rustica. The former cross is stated to have 

 resembled the original paniculata parent. In the latter case, all 

 seven more or less completely resembled the rustica parent, in 

 this respect resembling the behavior of the ten offspring of the 

 cross in Experiment 2 of the "Nachricht," [N. rustica X pani- 

 culata) X rustica, all of which throughout approached the rustica 

 parent, some more, some less. The compound crosses are not of 

 essential genetic interest. 



Kolreuter reports the results of a curious experiment to deter- 

 mine the possible neutral character of the stigmatic secretion. In 

 1760, he placed upon the still clean stigmas of a Ketinia species, 

 "drops of different natural and artificial oils," deposited the pollen 

 therein, and awaited the result; the flowers all fell off unfertilized. 



